I'm awaiting full details. Knowing the Volkswagen dealership, their standard line is 'before we can tell you whats wrong, and how much it will cost, we will have to strip it down and examine it' knowing they're pretty much giving themselves a blank cheque then, and the chance of you not going ahead with the work with them is non-existent.
Either way, if its new valves, I guess I'm still looking at £2,000ish by the time everything is taken off, checked, and the timing chain and the water pump and everything is replaced. And things this major should not be failing on a well cared for 44k mile car.