I think the Indian variant has been here for months in all probability, and just as likely to be brought home by British nationals or someone on business than some coming via Turkey.
Yes we still have some leaky airports, im not denying that, but i will say that by the time you notice a variant (as we did quite some time ago), it's already been here for a bit. And you'll never ever stop domestic spread until it's vaccinated. Cases are becoming more and more meaningless by the day. It's how the vaccines stand up to it now.