my old Job's head office was in Oakham, https://www.sarpech.co.uk/ is excellent I think that they have another in Leceister
Closer to home https://www.3room.co.uk/ in Ottershaw,Surrey is really good too
As someone of Bengali descent. if I want a Bengali curry I cook at home. Otherwise I tend to eat Curries at East African joints.
https://regencyclub.co.uk is my fave
https://www.zanzibar.co.uk is my wife's fave
Washed down with a few pints of Tusker