You should be able to drive it on a car licence, as it is a historic vehicle. There are specialist insurers for MV's such as Roadsure or Adrian Flux, who can be found through magazines such as Classic Military Vehicles or websites such as Milweb or even this very fine forum.
Accumulators usually require charging with an innert gas such as nitrogen, so a bottle and some guages will be required (Iam not an expert on Saracens, but used to work on Routemaster busses which had a similar system).
You would need to obtain copies of EMERs to get the srvice schedules for this type of vehicle, I am sure some of the guys here could help you out.....
A big problem with owning an MV is storage. Undercover is always preferable, and access to workshop/heavy lifting facilities is a bonus. If you have no previous mechanical experiance, don't worry as you learn fast in this hobby........