I've now been twelve months on this journey, trying to avoid the newbie pitfalls by asking lots of dumb questions.
I'm on my third mount, and haven't taken a worthwhile shot yet.
I have a HEQ5 Pro, a Losmandy side by side plate to mount a DSLR camera on one side, and a guide scope and camera on the other. I have bought a ZWO ASI120MM-S and a Williams Optics 50mm guide scope.
In the interests of stability I felt I should mount the 'scope directly to a 'V' plate instead of using the flimsy looking post mount it came with.
I've found, after two days of 'googling', that not a single manufacturer has a 'V' plate with the same drillings as the WO mount.
Now I can understand manufacturers not wanting to push business to their opposition, but it seems almost like WO have gone out of their way to design their mount to be non-compatible with Losmandy, Vixen, ADM etc.
If I wasn't such a tenacious old fart I'd go back to photographing birds, and forget about this astro stuff.