Thanks for all the replies. Sorry, I should have mentioned I have the Priority Pass for access to the lounges. I had a feeling I would not be able to get into Terminal 3 with a Terminal 5 boarding pass.
Thanks for the suggestion to visit London but on my way back I have a 19 hour layover so we will take advantage of that time to book a hotel and visit London.
Last edited by monsterdaddy; Aug 11, 2019 at 12:33 pm