You may approach the NRI cell of your State.

only after judicial orders are passed for his extradition, one may approach the high court seeking directions against the concerned ministry for extraditing him. there is no provision to cancel the nationality on the basis of a criminal case.

Your queries are confusing in the 1st place but i'll answer one by one.

1) Yes you can file a complaint against a british national if the offence has been commited in India.

2) You cannot get detail of the British national and cannot also get his nationality cancelled .

Mere filing of complaint may not be sufficient to cancel nationality.