The Weights & Measures of the Celtic countries is far too complicated to cover in any great detail here, but hopefully you'll get a flavour for the subject from these notes.
Ireland
From about 1450, the weights and measures of Ireland should have been the same as
those of England, but in practice the legislation in Ireland seemed to sometimes
be out of step with England. The act of union (1800) created uniformity, but of
course the Republic of Ireland went its own way again after 1922, on the formation
of the Irish Free State. From 1922 until absorbed into the European Union, Irish
weights and measures seemed to stay much the same as the Imperial system. Northern
Ireland of course stayed as part of the UK.
The ancient Irish mile is often quoted as 2,240 yards.
Scotland
The inch in Scotland and England were the same. The Scots ell was of 37 inches,
which may be connected to the 'London measure' by which cloth (etc.) was measured
by the yard and an inch (la alne et pous) in England around Henry VI's
time. The English ell was a yard and a quarter (45 inches).
The ancient Scotch mile is often quoted as 1,940 yards.
Wales
The measures in Wales are hidden (to me at least!) by the language. The
Welsh had measures of area called the 'erw' (which translates to 'acre'), the
'tyddyn' (='small farm'), 'maenol' (='manor') and 'cantref'(='hundred', as used
in English for a division of land, rather than 100).