Wanted - storage space for campervan in Oxon

Myself and a mate are looking into buying a Transit campervan in need of a bit of work, but I've no off-street parking, hence looking for storage in the above region.

I would need permission that I can work on the van at said place of storage, as well as use of 240v mains. Weather or not its under cover, I don't mind too much.

So if you can help or have any contacts, please give us a shout

thanks

David