Heathrow Terminal (probably) 3 is, from what I’ve seen, pretty much like any other big chunk of airport.
Go this way if you’re transiting, that way if you aren’t, yes the hallways do go for bloody miles, and here’s a queue to stand in.

Getting into the country was pretty simple, and a shorter procedure than the one at LAX; Then again, I think they’re actively looking to catch you out at LAX*, whereas all they wanted to know here was “On Holiday?”, so the line moved pretty quickly.
(* in 2013, the border control person asked me who I knew in Indianapolis, which kind of baffled me as a question. presumably my incoherent listing of a few names was enough to convince her that I wasn’t lying)

Baggage claim, conveniently, had my bag nice & obvious on the conveyor by the time I got there, and the crowds had died down enough that getting to it was easy; I’ve had times when the crowds are so packed that you can’t get to your bag, even when you can see it.

Following the signs led me to the Heathrow Express, which, conveniently, arrived at the platform pretty much at the same time I did, for a very quick transition to comfy seating & complimentary wifi. They have ticket-selling people who seem to have experience in dealing with the tired, jetlagged & confused, which made that process a whole lot easier.

Paddington Station is enormous.
Not in the same way as, say, Chicago, which had these enormous echoing halls you walk through to get to the trains; Paddington has a huge covered space, with a glass & iron arched roof, and it’s filled with trains & people & stuff.
A chap on the Heathrow Express platform saw me reading the signs, chuckled at my comment about getting my bearings, and pointed me at the end of the station where I could get an OysterCard. It took me a while to find the Transport For London … Not really a kiosk or store; It was a window in the wall of the access to the underground, but they were nice enough to explain the basic idea (Tag On at the first station, Tag Off at the last one, so much like the TransPerth system. Or perhaps TransPerth is much like Oyster?) and tell me that the card can be topped-up. (there’s a note about it printed on the little card wallet, so presumably there’s a decent number of people confusing them for being multi-trip ticket equivalents?)

I’d printed out the instructions on how to get to the WorldCon venue from their website, which included a very helpful annotated tube map. Unfortunately, the closure of access from Paddington to the Bakerloo Line meant that I had to engage with understanding the network slightly earlier than I’d planned, though signs pointing me towards taking the Hammersmith & City to get to the Bakerloo line at Baker St. eventually made me realise that I could do just that, and since Baker Street was a point of change on the route to the venue anyway, it’d all be OK.
It did take a while to find the appropriate platform, but I’ll be taking the blame for that myself, as I don’t think I paid enough attention to the signs. Got there eventually by reversing course along the Heathrow Express terminal, where I’d seen a “Bakerloo via Hammersmith & City” sign, which led me to the right place.

Wow, those platforms are narrow.
The above ground piers at Paddington were pretty big, presumably because of the number of people using them & the fact that they weren’t dug out, whereas the platforms on the underground kind of required that people stand against the wall to make it easier for others to get past. So, basically, manners.

Once on the tube network, it was all pretty simple, and I met a couple of other WorldCon attendees, Bob & Brigitte from California, standing waiting for the Docklands Light Rail at Canning Town; They’d already asked someone which train they needed, and while I’d figured it out from the helpful schematics, it was nice to hear someone confirm it.

Once I got to the appropriate station, I didn’t know which direction to go in to get to the hotel, so I climbed a set of stairs and looked for water, which worked surprisingly well, and the walk to the Ibis was uneventful.
There are a number of real estate agencies around here, which seems odd to me, and a few convenience stores or mini-supermarkets, which will be very convenient.

Hotel room at the Ibis London ExCeL Docklands is actually a bit nicer than I was expecting, with both working and quiet air conditioning (It’s a bit muggy here, especially on the Underground), and an unusually long breakfast-serving period starting at 4am for the early-riser set (which will be useful on the day I catch a train to Dublin, as I’ll have to get across the city during a weekday morning with a bag, so an early start seems like a good idea), free wifi, and a surprisingly comfy bed.

I figured that, after showering, I was probably going to fall asleep for hours, so I wandered out first to grab a bottle of water and at least look at the ExCeL Centre; Ended up being asked for directions to the train station by a group of somewhat lost Welsh girls, who weren’t sure where they were in relation to anything else. I decided not to tell them just how little local knowledge I had, pointed them towards the closest DLR station (according to the map, at least, and it looked a bit easier to find than the one I’d used; “Go that way until you hit the building, turn left, go that way until you hit a railway line”), and they left proclaiming that I was a ‘Lovely Man’.
Amusingly, to me at least, they were a mix of Asian & African looking people, all with strong Welsh accents.

Eventually a shower happened, followed by going to sleep at about 6:30pm when I realised that I couldn’t keep a coherent train of thought going, even internally; Random fragments of other stuff kept interfering.
I had planned to only take an hour-long nap, but that … didn’t happen.
Can’t even remember for sure whether the alarm I set went off; I think it did, but I don’t remember getting up to turn it off, just the ‘having gotten up’ part.