I'm considering replacing the speakers in the door for some new ones, i want them to be decent quality sound with good bass! but also not to much money! cheaper the better! £20-30 ideally! Thanks

I'd suggest you pop down to your local Halford store and have a listen to some of the speakers, unfortunately theres not much 'quality' about in the price range that you're looking for. If you find something you like the sound of you might want to go onto Ebay and see if theres anyone selling a set, the only downside to Ebay is you dont know how hard the previous owners have drove their speakers.
Good luck!