Probably another ZX headgasket gone but......?

[Gaskin]

I'll try and keep this brief since I suspect the answer is a new head gasket.
Last year had a radiator leak and overheated the engine. After new radiator no major coolant loss (~9 months to lose ~1 litre). No trace of coolant in oil. Some small bubbles in header tank when refilling cooling system and reving the engine, but nothing major. Rough starting cured by new glowplugs. This was ~10,000 miles ago. Recently it has started to leak oil somewhere at the front of the block. Initially I thought that the valve cover gasket was leaking so changed it (GSF one). Still leaking so nice new Citroen one (definitely better quality). Still leaking not as badly though. Oil seems to be coming from the top down the front but also seems to get worse around the join of the head with the block. In the last week things have got worse though. If I start from cold it starts fine and idles with a few very minor hicups. But if you leave it idling when the glowplugs go out it starts to miss badly and chucks out clouds of smoke that I think smells of burnt oil rather than unburnt fuel. Once hot it chucks a bit of smoke out every so often. There is no noticable smoke at high revs or on the over run.
So here are the questions:
Would a head gasket failure result in burning oil without coolant loss or pressurisation?
What further damage is likely if I just live with it?
If it is new HG time, and the head needs skimming do you need to dismantle the head or can it be done with valve etc in situ?
Anyone know of a good place to get a skim done in the Norwich area?
I'd rather not do th HG given the current outside temps and my lack of garage space, but if necessary I can. What else is worth doing at the same time? The current cambelt is ~30,000 miles old.
Thanks in advance for any help......
Cheers
Duncan