Thanks for the replies.
SiempreTuna: The 2nd hand idea is something I hadn't thought of. Might look into that. I've never had any problems with ebay but I haven't bought anything at that sort of price before.
Digital Controller: Samsung Ace is the one I have now which I'm having so many problems with. I've had Samsung phones before and they've always been fine but I really don't think I can forgive them for this!
dan330: Some good points there. I guess I could try rooting the phone again but it was such a frustrating experience last time... The thing about the deletable apps I do have is that I pretty much use them all on a regular basis. I believe the worst offenders with regards to memory are Facebook and MyFitnessPal which I use daily. In all I only have 8 apps which I downloaded myself, I used to have more but one by one they were sacrificed because of the memory problem. I sort of feel if I have to get rid of more then I might as well not bother having a smartphone at all!