Hi,
I too have been researching an ancestor in the British army in India. I've had some sucess in finding service records for him, there are two avenues to go down -
(You'll need a copy of his death certificate for these)
Contact the MOD to get a copy of his army service records. In short you can apply for his service records as he has been deceased for over 25 years. You have to prove this (que death certificate). There is also a fee for this service. £30 last time I applied for some records. It is worth doing, the amount of information revealed does vary though.
Full information and forms to fill in can be found here -
https://www.gov.uk/government/organisations/ministry-of-defence/about/publication-scheme#how-to-apply-for-records-of-service-of-deceased-service-personnelSecondly, contact the British Library Asia and India office. The staff I spoke to were kind enough to conduct a search to see if there were any files there which I would be interested in. You then have to prove the person is deceased and I think, explain why you want the records. In my case, I found service records for my ancestor who had gone from the British Army to the British Indian army (until the end of the British Raj in 1947) and then into the Pakistan army. The British Library had records of my ancestors time in the Pakistan army. I'm still missing service records relating to his time as an officer in the British Indian army.....
Take a look here...
http://www.bl.uk/reshelp/findhelpregion/asia/india/indiaofficerecords/indiaofficehub.htmlI don't know if you have seen these websites, could be of some help -
http://indiafamily.bl.uk/ui/home.aspxhttp://www.new.fibis.org/researchGood luck!