Hmmn. A 12-hour coach journey, you say? Perhaps someone should read this: <http://www.dft.gov.uk/stellent/groups/dft_rdsafety/documents/page/dft_rdsafety_504544.pdf>
It would seem to suggest that, in the UK, the max crew duty for a coach driver is 10 hours.
PS How one earth does one do that internet-linky-think?