In reply to TheDrunkenBakers:
> I've not had this before; do I need a special cable or anything for it?
Probably, yes. The socket you plug into will most likely be a 2P+E 16A Ceeform, so assuming you're camping in a tent as opposed to plugging in a van or a caravan, you'll want an extension lead with a blue 16A plug on the end.
If you're confident wiring a plug you could pick up a 16A plug for a few quid from somewhere like Screwfix or Toolstation for a few quid and swap it for the 13A plug on an extension lead yourself, otherwise you could buy a lead and/or adaptor from a caravanning place. The Ceeform connectors will tolerate a bit of rain as long as they're not actually lying about in a puddle, but it's important to make sure that any 13A plugs/sockets will stay dry.