Hi mjn
Just saw your message regarding the 2nd West York militia which you posted some time ago. I have a similiar problem in trying to track down the baptism of an ancestor circa 1811. Just like you I have found a possible father for him whom I know joined the 2nd West York militia at the beginning of 1812.
I had a look at the militia muster rolls at the National Archives and found that in 1812/1813, the 2nd West York militia were stationed at:-
1) Colchester Barracks
2) The Tower of London
3) Portsea Barracks
However, I didn't go back as far as 1811. I expect you have long since visited the NA and found the information you require but thought I would post this message just in case you haven't as your problem is so similar to mine.
Incidentally, this information still didn't help me find my ancestor's baptism - I'm still searching!
Hope you had more luck than I did.

Regards,
Ermin.