Found this webpage and has the regulations at the bottom of left hand side.
http://www.fuel-tanks.net/fuelbowsers.htm another page
http://www.hse.gov.uk/pubns/cdg.pdf
The driver of a vehicle carrying dangerous goods (other than explosives and radioactive material) in packages, which has a maximum permissible weight of 3.5 tonnes or less, currently does not need to have undertaken approved training and hold a VTC even if the load is over the Transport Category threshold. However, he/she will at the least need to have undertaken general training as per Regulation 9. From 1 January 2007, the VTC requirement will be extended to include drivers of vehicles of 3.5 tonnes or less. Note that the VTC is already (and will continue to be) required for drivers carrying loads of explosives over the Transport Category threshold regardless of the weight of the vehicle. Again, for loads under this amount it is still a requirement that the driver (and anyone else involved with the transport operation) received some kind of suitable training.
This was found on this webpage.
http://www.dft.gov.uk/stellent/group...ht_504701.hcsp
For bowser requirements why don't you chat to the makers as though you were a customer and get a brochure, this should have all the requirements in it.
JB