I would say the reverse, as in this country, many outlets look on the £50 note with suspicion, as their seems to be lots of dodgy notes about. We always take £20 uk notes (in good condition) We always use £20 notes rather than TCs and have never heard any outlet in India stating a preference for the £20 note. My own bank in Scotland have on more than one occasion tried to fob me off with £50 notes, mostly for their own convenience, I suspect.
Alan

I agree with gramps.
No way I would take £50 notes.
I would be really surprised if the money changers would welcome them at all.
A mixture of £20 and a few £10, try to get in clean condition without tears.

edit
just re read your post....no way will they give a better rate!
would you?

I agree, take small denominations that are clean and not torn - it'll make no difference whatsoever to the rate and you don't really want to be changing £ 50 notes up unless you need it for a specific reason. If you did two then you'd need a rucksack to put the rupees in as you don't really want anything bigger than a 500 rs note and mainly 100's. Untorn is important as the locals can get very fussy about a torn note. I've been told it's because they have trouble passing them on, even to banks....So never accept a torn note off of anyone either