Minibus drivers in the UK must follow the general rules of the UK Highway Code. However, there are additional rules for driving a minibus, particularly if you own a U.S. license. It is possible to drive in the UK with a U.S. license, but there are restrictions on the type of vehicle you can drive, including minibuses.
UK Definition of Minibus
According to the UK Department for Transport, the legal definition of a minibus is a vehicle that weighs less than 3.5 tons and carries between eight and 16 passengers---not including the driver. Anything more than that and a vehicle could be classed as a coach or bus.
Drivers with a UK Licence
Drivers with UK licenses granted before 1997 are entitled to drive a minibus, as long as it's not for profit. Trailers weighing up to 726 Kilogram are also permitted. There are different rules for minibus drivers that drive for "hire or reward", according to the Government Direct website. Driving for hire means taking money for driving passengers around in the UK. Drivers that want to drive for hire, or with licenses granted after 1997, need to pass a further test to attain a D1 PVC---passenger carrying vehicle entitlement. There are special allowances for anyone over the age of 21 driving for a social enterprise or non-profit company.
With a USA License
If you hold a full valid U.S. driving licence you are permitted to drive in the UK. However, this only covers vehicles weighing less than 3.5 tons, and carrying only eight or fewer passengers. You're allowed to use your U.S. license for up to a year after arriving in the UK, but require a UK passport to drive after that period.
It is possible to exchange your U.S. license for a UK version that enables you to drive minibuses. However, you will usually need to be a UK resident with a registered permanent address. You will also have to hand over your U.S. license in exchange for the UK one.
Speed Limits and Rules
As well as adhering to general UK road laws, minibus drivers have to follow additional rules. If towing a trailer, minibuses are limited to 60mph on motorways and are prohibited from entering the outside lane. Many newly-registered minibuses are being fitted with speed limiters that stop the vehicle from reaching speeds above 62mph. The driver must take responsibility for ensuring all child passengers under the age of 14 wear seat belts or child restraints while the vehicle is in motion.