The dealers work on a 12 unit per hour system in the UK, but even using that it'd be 3 hours (4.5 hours if you use the US units) - but of course they can have another guy doing the other jobs at the same time.
I've more recently spoke to a non-local (i.e. less untrustworthy) dealer and they said it'd 'around £450' for the clearances alone.