apologies if this has already been discussed. I am on QF1 into Heathrow, hopefully at around 6.30am on 8 November, with a transit before a BA flight to Dublin. The BA flight leaves T5 at around 13.30 and I'm hoping this is enough time for the transit bearing in mind QF1's atrocious delays. I am travelling with cabin baggage only. My question is will I be able to transfer from T3 to T5 without exiting and going through UK immigration? I am assuming I can check in online for both flights, which were arranged through Qantas on separate tickets.