If you are lucky, there will be normal meters and the supply will be on. In this case, just take a meter reading when you move in and phone up the supplier (it might take a few calls to find the right one) to ask for the suply to be put into your name.
If you are unlucky, there will be a prepayment meter in place, a deposit may be requested or the supplier may change the meter to a prepayment one.
You should start by taking meter readings, finding and contacting the suppliers, then take things from there. See below to find the current suppliers
http://www.moneysupermarket.com/utilities/energy-faqs.aspx#faq5