Thanks all for the advice!
@Starlight 1 - The new guide scope of mounted in a piggy back fashion, all firmly bolted down. Not even guide scope rings... And yes, I reset PHD2 to default settings and then set it up for the new scope & camera combo, so that all looks good.
@Owmuchonomy - Good to know that it's fairly common and nothing too untoward, hopefully.
@PhotoGav - Thanks for the binding tip, I had always wondered and worried if I'd over tightened things, but I've never heard any squealing, so if anything things may be too loose.
Good to know that I can try the RA worm gear adjustment without too much stripping down... I did follow the whole strip down process when I got this mount secondhand, just to check it out and clean out the default nasty glue pretending to be grease. But it's been a long time since I have looked at the guide. I shall attempt to give the mount some TLC over the long weekend, and test it out when we're next graced with some clear skies.
One thing that I did find when checking out the balance of things is that my DEC axis is very heavily out of whack... And I have no possibility to resolve it atm, I need to get an extra long dovetail so that I can shift the whole setup forward a bit. Right now the securing bolts are up against the saddle, and the scope is as far forwards in the rings as it can go... So a quick order to FLO incoming
Thanks again all, will update as and when I have any further news.