At that point, we were museumed out (either with tired legs or general art overload), so we went for lunch at a cafe called Angelina's (apparently highly recommended for its hot chocolate, and I believe rwrylsin will testify to that). That was quite pleasant, and fortified us for the return to the hotel to pick up our suitcase, and start making our way to Charles de Gaulle airport. Even that went smoothly, via Metro and RER, and we reached the airport in good time, browsed for last minute tourist purchases (rwrylsin ended up with some chocolate), and checked in and got our flight.
Here is where the problems started. During the previous night, my throat had been drying out (and waking me up with it), warning me of an impending cold. By the time of the flight, this had developed into a very sore throat, and blocked sinuses. My sinuses almost never get blocked when I have colds, but they chose this time to go, with two short flights consisting mostly of changes in altitude coming up. Oh joy ... and indeed, I struggled to get my ears to pop for all of the flight to Heathrow, and the left ear was blocked until well after we landed.
Ahhh, Heathrow. A blot on the world of airports. Two hours should be enough time to transfer between terminals, get something to eat, and get the next flight, right ? Getting from T4 to T1 took about 15 minutes (although it seemed interminable), but then we hit security going in to T1. About 350-400 people queued up, and only three X-ray machines operating. Simply ridiculous, and it took over 40 minutes to get through. At that point, we should have dashed downstairs to get something to eat in the "international" areas of T1, since there are a couple of places that have a tolerable range of meals (English pub food mainly, but that's sufficient when travelling). Instead, though, I forget that the domestic portion of T1 was devoid of anything except Costa outlets, and we joined the passport checking queue to head to T1. I got whisked through (UK passport, thankyou!), but rwrylsin had to wait, along with about 25 others, and wait, and wait. There were three people processing passports there, but anyone walking up with an EU passport got whisked through ahead of the "other" passports, and a few of the "other"s had complications (screaming kids and forgetting to fill in landing cards, mainly), holding things up even more.
That left us with about 30 minutes before our scheduled departure, so we moved on through to the domestic part of T1 - only to find that the flight was delayed by 40 minutes or so. Gah ! If I'd felt up to it, we could (probably) have gone back through the passport checkpoint and to the other eating venues, before going back through to the domestic area, but at that stage I couldn't face any more queueing. So, we devoured a couple of Costa paninis, and waited. Gate 5 was full, because it looked like most of the domestic BA flights yesterday were running behind, so we waited in Gate 6 for a while. Finally, it looked like some planes arrived at 5, so we went through and waited - then noticed people starting to head through the Gates 74-90 exit. Checked the screens and found that our flight was the one which had moved - at that stage, no announcement had been made over the PA system, and although someone at the boarding desk assured me that they'd made one, I remain unconvinced ... because they lost 4 passengers somewhere.
Yup, after getting all nicely boarded, they had to unload all the baggage (after waiting, and waiting), and hunt through for the bags belonging to the missing people, and then reload (waiting, waiting ...), and finally got us underway, about 2 hours late.
And of course, then we finally took off, and my poor abused sinuses decided they weren't going to play this game any more, and stayed resolutely unpopped (mainly on the left side) pretty much all of the flight. Finally staggered into Glasgow well after 10, waited quite a while for our bag, waited ages for the bus to the long-term car park, and finally went home (via a 24-hour ASDA to pick up essential bread, milk, etc).
Note to self (since I seem to keep forgetting): Avoid any flight plan which involves a transfer at any London airport, particularly Heathrow. If only the train option didn't cost so much ...
 Not literally, although leaping through the glass pyramid would certainly be a way of attracting attention.