Yes, you can, unless there is a covenant in your Registered Title or lease that prohibits it.
You can only drive the van across the pavement to reach the front garden if there is a dropped kerb, otherwise it is illegal.
It depends on the size of the van, if it is over 3.5 Tonne GVW then the owner/operator will require an Operators (O) licence. This covers where the vehicles are kept and the front garden of a domestic property would not be allowed, but if the house is also a business premises than it may be OK. If the vans are being run from the house rather than just parked over night then the property would require to have planning permission as business premises.