Ok, thanks for that heads-up, I've now updated the "my system specs" area, but to save you time, and answer your question,
I have a CWT Brand, PUFP305P PSU (305W) (Low, I know),
And mobo is: ASUSTeK Computer INC. P5KPL-AM IN/GB X.0x (Obtained from belarc)
Slots available (when looked inside) were, 2 White slots perfectly adjacent to each other, and the further up, slightly to the right, was a single blue slot. I hope this is enough information.
And finally, the budget was around £35, as It will preferably be a second hand Graphics Card I will be looking for, was just seeking advice for best bang for my buck I could get for that price.