Grahams right - because it's such a big job and nobody wants people coming back saying the head's failed a week after the work was done many places will automatically quote you for having the skimming work done - it doesn't mean they're trying to con you - it just means they don't want to risk it going wrong
I bought an earlier one (88) from a Lex garage years ago. Long story short:
Losing water, new radiator, losing water, do head gasket, losing water, skim head and renew gasket, losing water, replace head and gasket, job done.
Sales and service apparently split the bill 50/50.
It was about £1500.00 and that was a long time ago. Main dealer prices all the way.