Navigating LHR to catch a flight to EDI (T3 to T5)

The airport website has an entire section devoted to flight connections: https://www.heathrow.com/connecting-flights

Hopefully your flights are on a single ticket, because in addition to changing terminals, you will need to go through Immigration and security.

I did this transfer less than 2 weeks ago. You follow the purple signage for transfers. It’s a lot of walking. You end up getting on a bus that takes you over to terminal 5. Then you have to go through security. I forgot to empty my water bottle so had to wait for my backpack to be hand searched. Zippers on my pant pockets set off their metal detector - even though they didn’t set them off on my earlier flight out of Oslo - so I also had to do the pat down. Combined, the transfer from terminal 3 to 5 and security at terminal 4 took about an hour. Check the screens once you get to terminal 5. My flight was an international flight and they didn’t announce the gate until about 80 minutes before departure. If your gate is in the B or C area then you’ll have to take a shuttle to those. Nearly all of the food and shopping options are in the main gate A area.

Hope this helps!

The only difference between what Jenspur did and what you will have to do is go through UK immigration. There is a separate immigration area for Flight Connections. Follow the signs. If you are on a US passport, you can use the egates.

Use the Flight Connections link given in CJean's post for step by step instructions.

Thank you all for the information - the Heathrow link and the experiences transferring between T3 and T5 are very helpful.