Do please remember that buying any motor vehicle through eBay is risky, and campervans seem to be especially popular with scammers. There is no buyer protection from eBay, whatever happens.
Scams are often the work of organised crime (a senior police officer once warned on TV that one criminal gang alone had registered "multiple hundreds" of fake accounts on eBay for motor vehicle scams).
Scammers will always try to con you into paying for a vehicle before you have seen it. They find reasons why the vehicle isn't available for inspection, but can be delivered "on approval". You will have to pay in advance, but they will promise you that someone (usually eBay) will keep your money safe until you have approved the sale.
All these claims are untrue. So be careful, and remember that the safest method of payment for both parties is cash on collection after full inspection.