The name Hann is pronounced with the short phonetic 'æ' sound that one would automatically give it, were it spelt with a single 'n', (like can, man, van etc) - except in northern England, with its different vowel sounds, where it would be more akin to the phonetic Hən.  However many people when first encountering the name, wish to pronounce it with the long phonetic 'ɑ' of Hahn, thus leading to confusion with that particular family and an assumption that it is of German or Dutch origin.   Pronunciation may also account for the number of occasions the surname Ham appears in similar areas to the Hann surname, though with few exceptions both surnames seem to have maintained their separate identities - the odd Ham being recorded as Hann and retaining the name and vice versa.  Much of the way in which names were written down being due to the recorder's interpretation of what he thought he had heard or knew and the person providing the information's ability to read what was written and correct it if necessary .  Historically the Hann name appears to have been written as either Hann or Hanne and sometimes Hande or Han before settling down over the years to a standard spelling of Hann or Hand in the 19th century.  Within Dorset the Hann name prevailed in the majority of families, Hann and Hand being seemingly interchangeable in the Wootton Fitzpaine sub-branch and Hand being adopted in the  family to the east of Dorchester who provided the maternal ancestors of the renowned novelist and poet, Thomas Hardy

With there being quite a few Hanns in the US, family historians there tend to assume that all Hanns are of German origin, as there was a German family in Hunterdon, New Jersey from whom many are descended.  Nothing in my research leads me this conclusion however.  I believe that as many of their ancestors were either from this German family or were German HaHns they have often assumed that all Hanns were Hahns or German at one time, but the Hahn family seems to be totally unconnected with the Hanns until they reached the US and anglicised their name.  The earliest the earliest references in England that I have found to Hanns so far are to a Durand Hann in 1238, a Walter de Hanne around 1250 and a John Hanne in 1305.  In the same way that the Hahns of the UK have nothing to do with the Hanns. I also do not believe that there is any UK Hann(e)/Haun(e) connection - the only instances of the Haun(e) name that I've come across in the UK being transcription errors

There are Hanns in Germany and Austria, and many of these over the years have travelled to the US and are true HaNns, but if they are part of the same family who moved through past close ties between the UK and Germany, the fact that there are estimated to be over 2000 Hann households in the UK, whilst there are only 700 in Germany and 400 in Austria leads me to conclude that if related the 'German' HaNns are more likely to be a sub-branch of the English Hanns than the other way round. 

Members of the German Hann and Hanne families did travel to England during the Georgian and Victorian periods - in fact two Hannes fought at the Battle of Waterloo (one with 1st Troop, King's German Artillery and one with 4th Line Battalion, King's German Legion) -  but these appear to have been for short or transitory stays rather than settlement.  Only two Hannes (Henry William and Gottlieb) and one Hann (Andrew Walter) of German  Hahn origin seem to have still been here in 1911.  One of Henry Hanne's sons, John Henry, was later killed in action while serving with 110 Squadron, Royal Air Force in 1940.  The remainder of Henry's descendants are based in the Hereford and Worcester area and are not to be confused with the-Herefordshire Hanns (no 'e') who are distantly related to me.  I have been unable to trace either Henry's or Gottlieb's death in this country.  Saxe-Weimar-born Andrew Walter Hann was killed in action during the Great War serving on a British merchant ship. At the time, there was also a Russian-Jewish watch-making Hann family who settled in in east London and an Irish Hann family that settled in Hartlepool

My branch of the Wessex Hann/Hand families first appeared in the village of Dalwood in east Devon (then in Dorset) in the mid 1540s.  From there they spread into Devon and west Dorset, settling first in the village of Stoke Abbott, near Beaminster before initially moving to Broadwindsor and Beaminster itself, south to the coast at Bridport and throughout west Dorset from Beaminster and Bridport to the Devon border.

At around the same time that the Hanns appeared in Dalwood, two other branches were living further to the east. One in the villages of Nether Compton and Over Compton in the central Dorset/Somerset border area (first recorded in 1587). The other branch living in the villages of Henstridge (1569) and Stourton Caundle (also 1587), in the Blackmore Vale that straddles the Dorset and Somerset Border. Over the years this branch spread east to the Wiltshire border and south and west into central Dorset.

In the 17th century another branch of Hanns appeared in the south Somerset village of Montacute, near Yeovil (1643) and spread to the villages surrounding the quarries of Ham Hill and south west towards Devon.  There were also short-lived branches in Trent (1607) and Castleton (Sherborne) (1689).  These are both in Dorset, as is West Stour, where another branch appeared in 1743; though these are probably from the Henstridge family.

There were also Hanns appearing in the Northumbria region to the far north of England who were probably also the families in Berwick, Coldstream and Ayrshire (the Central Lowlands Hanns being primarily from Ireland) and in Bristol and the Bath and Mendip areas of northern Somerset.  Hann distribution throughout the United Kingdom remained the same for many years. In 1881, by birth of adult males, it was 54% Dorset, 20% Somerset, 17% Northumbria.

Over time these branches intermingled, with the Dalwood Hanns, Compton Hanns and Blackmore Vale Hanns of Dorset all moving to Yeovil in Somerset, where they mixed with the Somerset Hanns from Montacute and elsewhere.  Some subsequently migrating again, some to South Wales or London where they in turn merged with the mining Northumbrian Hanns.  Strangely this has resulted in the only Hanns in the Beaminster and Bridport areas today being from the Blackmore Vale branch.

From their original areas, the Hanns have spread westwards into Devon and Cornwall, northwards throughout Somerset and across the Bristol Channel into South Wales, east along the south coast into Hampshire, to the Drax family estates in east Kent, up to London and out into Essex, also to Newfoundland and other parts of Canada, Australia and New Zealand and throughout the English speaking world.

There were also Hann(e) families at Alcester and Acock's Green (from 1545) in Warwickshire, but over the years these became Hanns, then Hands and Hance and spread throughout the west Midlands.  Similarly a Hann family in East Anglia seems to have mutated into the Hunn family of south Lincolnshire and Norfolk.  It may be similar mutations took place with the Cornish Hann(e) family to produce the Hunn family of Calstock and Hanns family of nearby Lifton (across the River Tamar in Devon) and the Hanns/Hance  family around Helston, but none of these have been followed up as their origins are obscure

Certain male forenames were more common in one or other branches of the family, for details see

For an idea of the origins of the various families in the 1911 census see

WHERE LAND MEETS SEA IN W DORSET The small hamlet of Seatown, near Bridport.  Where the River Winniford (or Chid) makes its way between Dorset downs to the sea of Lyme Bay - typical west Dorset countryside