Mark,
Coming to this discussion a bit late, but the records are all in the National Archives at Kew. They are in WO 379/6 which gives monthly locations of all units.
I transcribed the period 25 December1802 to 24 December 1815, when preparing my paper on Authorised Establishments of the British Army 1802-15 which can be seen here:
I did not go back to 1798, but I am sure the accurate detail is there.
Rod