If anyone else is thinking of doing anything similar, stay in the T4 premier inn which is walking distance from T4 where you can take the tube for free to any other terminal.
@llamasoft_ox I've experienced that shit many times and on the last trip ( two weeks ago) we opted to stay in the Hilton inside the Airport. So easy, no stress, 10 min walk to terminal. Bliss. It wasn't cheap, but my heart and my head thanked me. And the roof top bar was great (also expensive!)
We all need a treat now and again.
@g7eix I genuinely thought I'd just be able to trundle from my car to the hotel. It was right there. Crazy that it took such a stupid energy wasting detour to go literally 100 yards haha