Well it's funny you should say that... The machine came without a pump, and it turns out the previous owners never had one. I thought this was down to lack of knowledge, you hear of machines being used with only line pressure from time to time.
So I bought a pump, got some advice on TMC and wired it up. Fine. Then whilst scratching my head over the plumbing I opened up the boiler to discover there is no HX circuit. The two vertical pipes are the pickups for the groups.

So with Jim's little clue, I'm wondering if indeed it is a steam pressure machine, and indeed what the hell that means, and am I going to get a decent espresso out of this machine if I continue the rebuild?
Thanks a lot, it feels like we're getting somewhere. We must be because my head hurts.