Buying cheap memory is often a false economy as if it fails you will need to replace it at a further cost. You say the PC isn`t worth £60 (the price of the memory) to you yet you are willing to put money into it. The PC must have a value to you, if it is not worth spending £60 for good memory, then why spend money at all?
Crucial guarantee their memory for life as do one or two others. Perhaps you should use the Crucial memory tool (it will tell you both the amount and type of memory you can fit) click here and then you can judge how much you may save by looking for a cheaper source. Once again I would add the rider about cheap memory.