Hiya Anne,
I received a reply from the guy on Belfast Forum. I hope the info. is of some help.
So far, I've eliminated the Royal Scots from the search. They left Ireland in 1799.
The 2nd Battalion, 42nd Foot (Highlanders), were in Ireland from 1804 until 1810 - I think there was a garrison in Armagh and one in Belfast.
The 73rd Perthshire Regiment is also eliminated - they were in India with the 1st Battalion - they had no 2nd Battalion until 1809.
1st Battalion, Royal Scots Fusiliers were also in Ireland - Belfast and Dublin, from 1800 until 1805. The Battalion was involved in surpressing the Dublin revolt in 1803.
The 2nd Battalion of the Regiment was only formed in 1804 and came to Ireland in 1806.
The 1st Battalion the 91st Argyllshire Highlanders didn't come to Ireland (Fermoy) until 1809. The 2nd Battalion of this Regiment never served in Ireland.
The 1st Battalion of the 93rd Highlanders (Sutherland Fencibles) served in Ireland from 1803 until 1805, when they went to the Cape of Good Hope for five years.
Again, the 2nd Battalion wasn't formed until past your dates - 1814.
1st Battalion, 26th Foot (Cameronians) didn't serve in Ireland until 1807. The 2nd Battalion wasn't raised until 1804 and came to Ireland in 1807 with the 1st Battalion.
The 1st Battalion 90th Foot (Perthshire Volunteers) did serve in Ireland from 1803 until 1805, but I can't determine where garrisoned, as is the case with the 2nd Battalion.
Neither Battalion of the Kosbies - the King's Own Scottish Borderers - 25th Regiment of Foot, served in Ireland at that time.
The 79th Foot (The Queen's Own Cameron Highlanders) also had their 1st Battalion in Ireland from 1803 until 1805. THe 2nd Battalion was only raised in 1804 and didn't serve in Ireland.
I think this covers all the main Regiments of Foot - although cavalry and yeomanry aren't included - they didn't generally serve overseas as they were locally raised.
Sorry the info doesn't narrow the search much further but hopefully will be of some help.
Chris