Presently I have just painted over my yellow wall with some white matt paint in a 225cm x 125cm rectangle and then tapped some 3 inch black duck tape around the edges to make it look like a 'screen'. I will probably add a black curtain rail or something to make it looks more impressive.

I cannot afford a dedicated screen and wondered how much i am missing in the picture quality department. Or infact if there is another cheap option that i could take to make a positive impact worthwhile. Dont get me wrong i am happy with my picture at the moment, but then again i am new and do not know what quality of picture i should be expecting. I would entertain a change to my set up, but only if there is a noticible picture quality difference and not just a small tweak.

Regards

Without reference, it is hard to judge quality. While your wall may deliver an ok picture, try this : tape a sheet of printer paper (bleached) on your wall. If you see a big difference, then most likely you will benefit from a screen (even if it's a homemade one , like painted MDF or a rollerblind cloth screen.) Commercial screens tend to perform better still.