How much gas n electric combined do u pay per month? im one person in a small flat?

im with edf i just started the allegedly cheaper online tariff. im being charged �80 monthly for a one bed flat with 2 radiators..is this too much or average..im �140 in credit but they wont refund me and are taking �80 in 2 weeks time..surely they should refund me if i ask? also will i get a charge if i stop the elec gas online tariff direct debit and go back to standard tarriff?