Turns out the place has a pay-as-you-go meter and once we found the key in the kitchen we got the power on.
I've spoken to the landlord and the electricity supplier and the meter is going to be changed next Monday.
This leaves me in a state of not knowing quite how much electricity I currently have (I'm sure the meter would tell me how much credit was in there, but I'm not sure that would help me figure out how long it would last me), so I'm now waiting to see if the lights go out between now and Monday.
Given that I have candles and a camping stove with plenty of gas, most of my electrical stuff (hifi, computer, etc) is still packed in boxes, there's very little in the fridge-freezer, it's not been cold enough to switch the heating on since I moved in and I'm away in Exeter Friday-Sunday, at what point does it just become not worth topping up if it runs out?
I guess I'm on silent running for the next few days to see how long I can make it last...