[pmac]

I was reading through one of the links that Chumby put up - the Legal one, and found this which is very relevant for those wanting tyres and a lift:

Raising the height of the vehicle may be performed without certification providing the overall increase in vehicle height is not more than 50mm. This may be achieved as a single modification such as the installation of a 50mm lift kit, or by a combination of smaller lifts as described below:
 the fitting of body blocks or lift kits (50mm maximum if no other modifications resulting in a change of vehicle height are performed);
 suspension modification, (50mm maximum if no other modifications resulting in a
change of vehicle height are performed);
 changes to tyre size (maximum change in tyre size diameter of 50mm); or
 a combination of the above that results in a change of vehicle height not exceeding 50mm.