Thanks, all. On reflection, (and pace Dick) I think the sky is rather overdone. I'm not really sure how it got that way, though: the originals that I fed into AutoPano weren't so saturated but on restoring the ProPhoto profile to AutoPano's output, bang! Trying to reduce the saturation gave weird-looking dark haloes around the clouds. There's too much of this photography stuff I still don't understand.
Anyway, here is a revised version, with rather more natural-looking (to my eye) colour: I've also used cylindrical rather than planar mapping, which I think gives a more accurate result.
Dick, I've attached three 100% crops, from the extreme right, the centre tower and the tower at the rear (the latter two are attached to my next post because of restrictions on the total attachment size).
Jeremy