Actually, I suppose what I ought to do is to expose any 'errors' to assist.
So here goes:-
1) Front brake needs longer 'nut' to go through carbon steerer - forgotten that before when I was building my racebike, but it's a standard part and was £2 from LBS
2) Had mental block about which brake went to which lever. Quick check in the garage on existing fleet helped with that one.
3) Cutting the steerer. I did the right thing which was to 'go too long' on the first cut, and I'd underestimated the thickness of the top cap, so it was about 2mm too long to get any compression with all the spacers in place. So had to do a second cut 5mm down to get the compression. No problem, just meant double the cutting and taking out the fork again as I didn't want steerer dust falling into the headset bearings by cutting on the bike.
4) The thread on the driveside of the BB was a bit rough which meant that the bearing wouldn't screw in straight, and in fairness it would have been very easy for someone to have just tried to force it and cross threaded it. As it was, as soon as I couldn't tighten it by hand then I knew something was wrong and so backed it off, cleaned the swarf out with a small electrical screwdriver and then it was fine.
5) Anti seize used on the seatpost, bottom bracket and pedals. Chain de-glooped before putting on the bike.
6) Don't use the full chain length, put it in largest at front and rear (I know, you don't use in real life) then fit chain with overlap 2 links with mech at limit. This means you can't pull the mech off if you get the chain diagonal when out on the road.