Advice on buying an electric Guitar.?

My 13 year old son has been playing guitar for a year or so. They have an acoustic guitar and an electric guitar. Their electric guitar is a bit unreliable. It is worth about �65 (from Argos). He has been pestering me about getting a new one for some time now and I sort of agree but I don't want to blow the budget. Can anybody help me get ideas on a reasonably priced but reliable guitar that I can buy in a UK music store (there are a few nearby).