I remember when i was in UK, i got my docs notarized from my Bank Natwest, all i did was went to the base branch and showed my original on the counter and they notarized stating it is a true copy or something like that cant exactly remember the wordings.
Hope this will help.
No point paying 700-800 pounds or else if you are indian national why dont you come to india and get it notarized with that kind of money