Thanks Andy.
For the benefit of others the gist of Andy's reply is that my mount's behaviour is not typical, although I have read on CN many reports of them needing adjustment by loosening the three screws on the top of the azimuth bearing, adjusting the plate and then tightening the screws again so that the gears mesh correctly. I've done this myself and it helps to eliminate the usual backlash but not my tilt problem, which probably needs the mount to be taken apart completely but I haven't been able to do that due to a lack of DIY skiils.
I may try to acquire another one in better condition and sell the current one to a tinkerer.
