Wheel truing - Help removing wobble, flat spots, etc

Sounds like a dead rim... and replacements are not cheap :-(

if it's a new rim and the bike shop can't get it round, try another bike shop? 3-4mm is quite a lot, is there a low spot opposite the bump where you could reduce some spoke tension?

It's unfortunately okay around the rest of the rim, so I'm guessing that it's dead. It's gone to another shop, who've confirmed it's knackered, which is a shame as somebody's tried to put a new rim on, and er, failed.

Oh well, I'll return them. Thanks for the advice. :-)