Having had my Samsung 2433BW display since March 2009, today the display has "interference lines" as well as swirling colour patches moving across the screen untill i cant see anything at all on it. Ive switched it off and on again and its fine for about 3 or 4 mins then it starts again. The display does it without the PC connected and im using an old monitor to type this.

Have you any background on electronics? The problem actually could come from a leaky or defective capacitor in the inverter board of your monitor. If you know how to actually open up your monitor the capacitor will look like something 'bloated". But if you don't actually know electronics and don't know how to open up your monitor i would suggest bringing it on an expert rather than you doing it and end up making more problems.
A capacitor should look like this:

a bloated one should have its top side almost like a dome not flat as it usually looks like.