Hi Sue
If you search for Edward Birch on the NA Catalogue, using WO for the series code, the top one might fit -
http://www.nationalarchives.gov.uk/catalogue/search.aspMen would enlist for life then, so he may have been injured or no longer required after the Peninsular War ended.
The reference starting WO97 is a microfilm in Kew. You can request a quote for them to send you copies but they have been dragging their feet, as they used to charge only 40p a page plus postage. You may have to go yourself or use a researcher - they have lists. Or Findmypast will be putting pre WW1 records online 'by 2011'.
You also have to realise that records to other Edward Birches have been lost. The army also did not record family history information then.
http://www.nationalarchives.gov.uk/militaryhistory/army/step4.htmThe medal roll for the Peninsular War shows a Edward Birch awarded a Military General Service medal with clasps for Vittoria (21 June 1813) and Orthes (27 February 1814). The medal was not authorised until 1847 and men had to be alive then to claim it.
http://www.northeastmedals.co.uk/britishguide/militarygeneralservice1793_1814.htmI would try to find a local newspaper at the time of his death. It may give details of his service.
Ken