* Chauffeur service (at both London and Bangkok) - any point in booking early?
Certainly book as soon as possible and reconfirm 48 hours before too. Lest they have any reason to make an error, which can happen.
* Our trips to LHR will be from different places in London - can we book two cars for each of us, on the same booking?
Of course.
* Is the LHR lounge a 'destination' i.e. worth getting there early? Bearing in mind our flight is at 09:00 and I don't want to get up in the night just for an extra glass of fizz
Not worth it. Its a reasonably good lounge, but given the time of your flight I wouldn't. They have a spa, which is good but paid for J passengers.
* Our connecting flight time AUH-BKK gives us just over three hours in AUH. Any general lounge tips, showers, games, spa? Linked to this, are there any eating options or is it the one restaurant in the lounge? And, is it worth it? I don't mind paying for a nice meal in the terminal if it's worth it, over and above getting sub-standard food 'for free' in the lounge (if you fly BA you'll know what I mean)
The EY lounge in AUH, is about the best place to eat in AUH other than the F lounge. Showers are good, the wet shave is worth the money, as is the spa. Breakfast tends to be better than late evening food in the J lounge.
* What are the BKK lounge arrangements? - are EY still utilising the Thai Royal Orchid lounge? (which I've been to and know what it's like)
No longer Thai lounge, a very bad lounge in BKK, get there as late as possible.
* Our return flights give us just 1h 5 mins connecting time in AUH. Although that will be enough to connect, will the flights literally be close to each other so not a massive walk? Would that amount of time give us any usable lounge time, even if just 10-15 mins for a quick drink and freshen-up?
In relation to the flight/onboard experience:
It varies, sometimes BKK land in T1 sometimes T3. LHR flights almost always depart from T3. I don't think its enough time to be honest.
* I've booked us in 10EF on the LHR-AUH leg (A380), then 7EF on the AUH-BKK-AUH legs (2 class 777 with 10 rows of J). Then, 20EF on the AUH-LEG leg (no J 'couple' seats any further forward). I assume these are the 'best' for a couple - we do want to sit next to each other and be able to communicate
It's not that easy to communicate even in those seats, and the middle seats are tighter than the window seats. I'd go for the window seats.
* The flight times mean three out of four legs are daytime flights, with just the AUH-BKK overnight. I'm assuming there are two full meal services on all sectors? Is it dine on demand? Anything EY does particularly well/worth asking for?
EY is always dine on demand, but many crew will try and make you order with everyone else, just tell them when you want to eat and be firm. Also, I can't say any of the food is amazing, but good dishes in J are the steak sandwich (snack) and some of the desserts.
* I'm assuming they provide amenity kits on all legs? How about PJs?
Amenity yes, Pajamas no only in F.
* Do they provide a turn-down service to make the seat into a bed, or are you left to your own devices? Not just for the night flight, but on at least one of the return legs we're most likely to want to sleep pretty much the whole flight sector
Can't remember, I don't think they turn down in J, in F yes they do.
* Any other tips or hints worth sharing about the EY experience? I've flown a number of other airlines, and as mentioned, BA more times than I care to remember. So I'm keen to understand the comparative experience
Its worth stopping a night in AUH. They give you a free five star hotel for one night with a paid J ticket. As you are two passengers, you can get two nights. Although they do sometimes try to make a fuss giving two nights, but you are entitled. The arrivals lounge in AUH is great, free wet shaves even for J passengers and free clothes pressing while you shower. Then you can go to your hotel in Abu Dhabi, with included return chauffeur transfers. Rest, have a meal at your own pace, enjoy the weather and views, as well as a luxurious hotel, and head back for your connection.
Compared to BA, EY service is usually considerably better, and the planes ex LHR are 1000x better. The Business studio seats are great. EY has an onboard lounge in the A380 which is nice for a drink or two, but not quite EK or QR's bar. EY plating and crockery/cutlery is very nice, but the food is so so. They've switched recently to Billecart brut in J, which is probably the best Champagne in its price bracket. Other things to note are that the hot towels smell so good (rose), an the BKK flight will be a big disappointment after the LHR A380 flight, however its not that bad compared to other airlines.
Another thing to note is that in my experience in J on EY, you're not treated as premium really. The AUH lounge can be very busy and has no table service (LHR lounge does but what comes out is rarely that good), not all but some crews, mostly on 2-3am flights will ignore as much as possible, because they think everyone is sleeping. This is in comparison to airlines like ANA, which treat their J passengers very well. Although, you said your benchmark is BA, which don't even treat F passengers very well...