Pulled the plane out again this morning and did another start - thanks to @nomadpete the oil pressure gauge is now working.
I bought a small fuel tank (generally used for working on motorbikes when the tank is off) and suspended it on one side of the fuselage going into the wing tank inlet to the header, put a couple of litres in then switched the line to the return barb for running. (Forgot to take a photo sorry).
Ran it for about 10 minutes. Look like the oil TEMP gauge is not working now, so will have to try to figure that out. (or ask Peter to help which is more likely to result in success!)
Kept it at 2000rpm for most of it, after running around 5 minutes at 2000 and with the oil pressure stable on around 3.5 bars I increased throttle to 4000rpm for around 30 seconds, then tested magneto drop individually. Then back to 2000 for another few minutes. Idle with throttle pulled back as far as it'll go is around 1800rpm, at that point oil pressure is reading just under 2 bars.
At the end of the run the CHT's are showing around 75 degrees on one gauge and just on 50 degrees on the other. I'm assuming the lower temp is on the front cylinder, will have to trace the wiring on that (and then label the gauge!)
I need to tighten up a few nuts in the oil system, there's a slow drip from the bottom nut and I think also the oil cooler connections.
The other problem is one of the main gear tyres went flat - it always had a very slow leak but now you can hear the air whooshing out of it when you take the pump off. I reckon the valve stem has a leak where it joins the tube - will have to undertake the painful process of replacing that (it's a Savannah wheel which splits, I've heard they're painful!)