i'm using a 19" LCD in my cabinet. at first, i bought a piece of posterboard at walmart. I don't know about in the UK, but in the US, posterboard is available at all kinds of places. I cut it to the right size and spraypainted it black. it worked pretty well, but i wanted something that looked a little nicer. so i masked off the screen area on the plexiglass that covers the monitor, and spraypainted the back side of it flat black. from the front, it looks very glossy and smooth, I am very happy with the way it turned out. now the only problem is that the monitor casing is silver, so i need to remove that and paint it so you don't see that tiny silver edge.
here is the posterboard bezel:

here it is with the plexi painted black:

there are some smudges on the plexi, but you get the idea. the best part was that it was very cheap to do. the plexiglass cost me about $8, the paint was $1, and i already had the masking tape.