The original poster is asking about taxiing to get fuel with a passenger, but without a PPL.
I often taxied out to get fuel by myself when I was training (boy did I love that independence!), but always by myself. I'm not sure where you stand legally with pax, but personally I wouldn't do it. If something goes wrong, there's going to be a lot of questions, and you may not be covered by insurance for their injuries/aircraft damage, let alone what the CAA thinks.
Also, why do you want to take someone to the middle of an airfield to stand in the cold and wind, while you refuel an aircraft?