That is true but a significant subset of these British-Indians are Ismaili/Gujarati Muslims from Africa whose ancestors settled there few generations ago. They were born in Africa and only identify with British India.
Hindus 558,342 + Sikhs 336,179 = 894,521. While 97% of Pakistanis are Muslims so 905,700 will give you 878,529. That means Pakistanis and Indians are nearly equal in UK. These are all my interpretation and I accept that they are neither scientific nor completely accurate.
It may not be your intention, but I think it was very unfair on your part to club all muslims in UK as Pakistanis!
I have a close Gujarati Muslim friend (working for an Indian IT company) who was born and bred in UK with his parents migrating from Africa. He and his family, all of them, consider themselves to be Indians.