If you want a decent curry... jump in a cab and ask them to take you to Mangla... he'll know where it is and here's why i reckon it'd be good
Taxi there and back up to £8 (Black cab, you can get a private hire for cheaper)
Food.. free poppadoms and pickles, two curries, chapattis, rice etc... £10
Take your own booze or water there is free
Job done ;-)
There aren't many cheap curry houses in town. You need to head a but further a field i'm afraid
PS You could even jump on a bus... but i'm not sure which one tales you up to Spital Hill.. or back (help anyone?)