What Leave to Remain is it? FURTHER or INDEFINITE? Did you use that English certificate for ENTRY CLEARANCE in the UK?
I'm open to any correction if I'm wrong, I can't see why KET won't be accepted as your proof of English Language Test.. Only TOEIC/TOEFL are no longer acceptable as it's just recently removed from the list of the approved English language test....same with ESOL skills for life of Trinity college and BULATS which will be removed too from the list on the 1st of August.