Thanks Bill! And thanks again for advice and encouragement along the way.
The second gear stubborn behaviour was caused I think by the new synchro ring sticking to the gear. I noticed this whilst playing around before the cover went on. I let the car coast at about 35 - 40 and switched repeatedly & gently between 4th and 2nd (not something I'd normally do...), listening for the "whizzz" as the gear sped up on the synchro before engaging. That seemed to bed things in a treat. We'll see on the next start up from cold.
I'm really happy & pleased to get something like this under my belt. In some ways it was more tricky than the engine rebuild, but also very rewarding.
After running for about 1000 miles on straight 30wt oil, I finally changed to 20W50 non synthetic, plus some anti wear additive. Pressure is 60psi at idle and it pulls like a train. Loverly!
Ed
I want my MGB