Well to answer my earlier query regarding coolant, quite a bit of air came out on the first round of bleeding I did this morning. Ran it and letting the coolant temperature drop now before having another look later.
Almost makes me wish I had the electric pump of the N52.... almost
Edit: Also think the CCV may be blocked and in need of replacing at some point. Seems to be burning around 1 litre every 2k miles right now, and there's no leaks or mixing with coolant. No blue smoke from the exhaust either so it must be small amounts getting blown into the engine.
Might leave it until I'm off around Christmas to be fair, two weeks sat round with the Mrs at work seems the ideal time, assuming it's bearable to be outside!