Ah, sure enough. 3rd, 4th, and 5th frets were up just a tiny bit - some judicious tapping with padded devices (tiny bit at a time) brought it back to acceptable. It also brought the 3rd up a bit at the D string (or I just hadn't noticed it yet since I play my 4-string WAY more than the 6) but that was also easy to bring down gently - played through all six strings from open to eighth fret - I'm sure a pro could get it to 'amazing', but I got it to 'okay - better than it was' without doing any harm, and there I shall leave it.
Someday soon I'll try to get it in for a proper job, but the guy I trusted most locally is semi-retired and hard to get in touch with.