I'm up in Stevenage - not far from you - and would be happy to help you do it next weekend if you feel up to it.
I've done it on my 2.6, following the DVD every step of the way, having never done mechanical work before, and it's easy. It took me about 4 hours from start to finish.
You'd need to get hold of a V6 cambelt locking kit, though, as I don't have one -
Autovaux will hire them out for £100 deposit and £15 hire charge. They can supply you with the right cambelt kit, water pump and aux belt too - if I remember correctly it cost me about £200 in parts to do mine.
If Vauxhall do charge £300 that's not bad - but does that include parts?
EDIT: Just read that yours is due in 10k miles - in which case you won't need it done so urgently! Either way, I'm local and happy to help if you wish. Just drop me a PM when you're ready.
2nd edit: The £200 in parts figure included the cam cover gaskets too - so a cambelt kit, water pump and aux belt would have cost about £130. I really must check my facts before posting...
