Mine was quoted at £300, when I got there to pick the bike up it was only £260....
... and then I noticed they had not done the plugs which were quoted for, in all fairness they offered to do them for free the following weekend, and I think I now know where the costs come from, the plugs are utter bastards to get to, it took the bloke over 2 hours just to change the plugs.
I reckon it probably is about four hours labour if following the schedule properly, and oil / filter / 4 plugs is going to take it up to about £300 at most main dealers. Apparently the plugs have an odd NGK number (extra digit I think) but only because they require a different gap and you can fit the cheaper versions and re-gap them.
I will do the 18k myself as it is fairly easy (oil / filter / tyre kick) and then get the tappets done by my local indie as he is @£25 per hour cheaper - which adds up on a 6 hour service.