My Canadian cousin is travelling via London with a 5 hour stop over, landing at T3 and exiting T5. Can I meet her for a coffee landside in T5? She won't need a visa.
I do not exactly see the problem here. What are you asking? Is five hours enough for your cousin to go through UK immigration, transfer between the terminals, check in again and go through security? Sure, that's plenty. Yesterday someone asked whether 2:35 is enough and I went through and showed it's tight but 5 hours is aplenty. What other concerns are there? Is she going to be allowed in the country for such a short time? As she doesn't need a visa, there really can't be a problem, just tell the truth. I have entered the UK for a similarly short period of time to run to Harrods to pick up gifts (my sister-in-law is particular to a fudge only available in the dessert hall) and noone bat an eye. What else... Are you allowed to enter the Heathrow terminals if you do not intend to fly? Sure.