Thanks for the advice guys. I didn't touch the bleed valves at first, I just emptied out coolant, put hose back on, refilled (it only took 3.5L, can't have got everything out), turned on and it only went up as far as 85. It normally goes straight up to 90 and stays there. (I'd always assumed 90 was when the thermostat opens, but this can't be the case as the radiator fan was on once it got to 70!) I could see the bubbles coming through the small pipe into the header tank, and the level dropping accordingly (It was well over max, and it dropped to max once it got to 85) I turned it off and opened heater pipe bleed valve, hot water came out. Couldn't open rad bleed valve, was stuck fast.
Turned it back on and went for a run to the petrol station (about 1/2 mile) and it went to 90 and stayed there.
When I got back I went around the block (still at 90) then turned off. The level was just above min. I took the cap off, pressure was released and level went up to above max, then dropped again instantly to just above minumum.
I assume this was the air coming out.
Have I done it right??? The engine smelt very hot after the run, but the temp was at 90... Plus I've never really smelt the engine before