mj9 wrote:

what are the symptoms? and how much are we talking? (so i dont take a heart attack when i get the bill!)
First of all you have to ascertain there is HGF. You also have to decide where to get it fixed. JPS and SLS are going to be a lot cheaper than MMC, but you pays your money and takes your choice.
Once you know that you have HGF just to replace the head gasket and perhaps give the head a wee skim is the best case scenario.
You would change the cambelt and tensioner at the same time, unless you had it done recently (this saves getting it done when it's due which makes the next C service a bit cheaper).
On SELOC, this is commonly quoted as costing between 500 and 1000 quid depending on who's doing it and whether or not the head needs a skim. Often people say 800 is the minimum it costs to get it fixed properly, but I don't know where that comes from ... anyway, that's SELOC pricing ...
If the problem was originally caused by low liner heights (unlikely on your car I think) then the engine needs to come out and be stripped down - you then need to get the block machined to correct the liner heights and then rebuild. An alternate to this is to buy a replacement bottom end or low mileage second hand engine. Either way, it's going to be a lot more expensive than the HGF repair alone because of the extra labour to remove the engine.
Cheers,
Robin