There are many more FT than me at LHR so this is from a non FT at LHR. I fly YYZ-LHR-EDI. Around 3-4 times a yr. Usually land 07:05 and connect to EDI around 2hrs later. I have an EU passport and fly CW so the fast track EU passport control T5 is suposed to help. Often doesn't. It can take anyware from 30mins to 90mins to clear passport control and get back through security and I believe you need to go through security again at LHR. If not someone please tell me cause I've been doing it wrong ! If BA allowed the booking on one booking you will be looked after. I have made a 90min connection to EDI and had a bit of time to spare and I have missed a 90 min connection so it's doable but the issue is clearing passport and security in 30 mins. Don't worry though on my missed connection BA booked me on the next flight no hassle at all