Right, a longwinded update.
Did I say earlier that simple though these kits appear to be, they can never be taken for granted? The last few days have been beset with self-inflicted problems: a classic case of more haste, less speed. I managed to smear epoxy resin over one side and both ends for starters. Don't ask me how, I just did. Fortunately it was the varnished side that was messed up and several very quick and light passes with a tissue soaked in IPA solved the problem. The ends were treated similarly and survived, although they will be resprayed.
Attaching the second side and inserting the wheel sets led me to believe that there would be no further problems. The body is square and sound but a trial run on track, once the adhesive had dried, showed an appalling wobble, something I could not live with. This had not surfaced at all during the earlier dry run and was a puzzle until it was traced to one of the wheel's plastic insulating bushes. The wheels are at least 50 years old and at some time, during their attachment to the coach, a bush had cracked and the wheel had shifted out of true, irreparably so.
The frames are rigid as you can see and the body parts are glued solidly together. The only way to remove the wheel set was to cut through the axle. This done, a new set was cut into two [and the centre piece further shortened] and then long tubing from an unused pop rivet was cut down, reamed out and slipped over the cut axles with both wheels then pushed in. In that way, the wheel set could be inserted into the axle boxes and a back-to-back gauge then used to pull the wheels apart to the correct setting. Liquid superglue was then applied to the tubing and capillary action drew it in, securing both wheels firmly in place. The coach now runs without a wobble. This palaver took an entire day to sort, the main problem being sourcing a metal tube of the correct dimensions to form a whole axle. The photo is probably worth a thousand words however....

Pop rivets are available in a number of sizes and provide a valuable source of cheap metal tubing for jobs similar to this.
Finally, a photo with the roof dry-fitted to check for squareness, etc. I have repainted the roof and it awaits re-application of grey paint below the rainstrips. Buffers and couplings have also to be fitted and a little touching-up applied here and there. But coach one is now nearly complete.
The glazing of the roof lights is quite effective I think, certainly worth the effort.

Comment has been made elsewhere about avoiding Keyser white-metal kits. Certainly, their loco chassis can be trying, and their motors are probably best avoided completely, but for interesting prototypes like this they really are worth persevering with. If you've patience and the right tools, an acceptable outcome is nearly always possible.
Tony