I'm looking at SFO-LHR-IST via a combo of BA and TK.

If memory serves me right, SFO-LHR should put me in T5.

If I'm reading the pages right, LHR-IST will depart from T3.

I know that they recommend a minimum of 2 hours to transfer.

But here's the catch: I have bags to check-in.

How will this work? I'm pretty sure I can't interline given OW vs *A. Will I need to immigrate into UK to make this connection? If so, do I need to budget 4 hours to pull this off?

Would you attempt something like this?