The monitor is the last part of a computer to skimp on, owing as it's the bit you hook your eyes up to.

Sorry - you will not get a 19" that is worth using for £150.

I'd personally take a decent 17" monitor over a 19" cheapy any day.

If you're on a budget Monitor Warehouse are OK, I use a 17" Dell Trinitron from there on my desktop, and have sold several on.