He's serviced mine twice including a cambelt change and sorted out brake issues when I managed to flood the master cylinder with air. Nice old school garage and prices seem to be very fair, couldn't recommend him more.
They're a fantastic outfit, looking after a few of London's 4Cs and 8Cs amongst others. They say they're a performance Vauxhall specialist but they look after all sorts of exotica, although the 159 shares enough Astra/Vectra/Insignia components for them to be familiar from their VXR work!
It's easiest to contact them via email, they're just so busy that the owner is very difficult to catch on the phone.
Tell him I said he'd sort you out with a decent price.
It started with a recommendation from the rescue service driver and an emergency battery replacement. I've had two full services since. I'll continue to use them, as they're friendly and accommodating.