Thanks both of you!
I'd assumed that it was essentially a box of buttons with no smarts - I'm quite pleasantly suprised that it talks serial of some flavour between the mount and handset.
Is the protocol known/available?
I've found this:
https://code.google.com/archive/p/sk...rProtocol.wiki
But i'm not sure if it's relevant, as it mentions GOTO in the command set.
I've got an assortment of rs232/ttl and level convertors lying around, so if the protocol's known, i should have everything i need to DIY a PC interface.