Sockets are the round two pin type.
As you can see in the above piccie, this is what we used to use for Houx. The orange lead is an external type camping cable with the standard exterior round sockets (one male, one female). You then need a two pin plug with female round socket as seen towards the top of the picture. This is what plugs into the hook-up. And we then use a male round socket to standard UK three pin plug socket into which we plug an RCD. These can be seen at the bottom of the pic. We then plug 4-way extension leads into this.