Now back, I can confirm I took the 7D after all.
It was interesting to compare the paranoia of different airports, and I do wonder if Heathrow is one of the more relaxed on carry-on security scanning. I think only once ever have they ever stopped me, and asked me to turn on a laptop.
Bristol airport did further examine a LED torch I had on my keyring, and returning from Munich, they checked the 7D and lens out (turn on body, and they also wanted to look through the lens). In hindsight I could have been cheeky at that point and asked to take a photo of what they look like in the scanner... would be interesting.
And for no reason that I'm aware, both entering and leaving Germany I'm sure the passport examinations there picked me out for a longer look than most... is my passport photo that bad? I took it myself... but got accepted anyway
Side note: do airports no longer ask the "did you pack the bags yourself or could anyone have tampered with them" question? I did not hear it at all on this trip.