have you thought about refurbished, and get what you need for less than half the outlay?
Your requirements are relatively lightweight.
If you don't mind a few scratches and (probably) WinXP rather than Win7, and being your own support desk, a refurb system (maybe with refurb monitor) would save a fortune.
A well known name to start with would be
www.morgancomputers.co.uk - I've bought a variety of the HP/Compaq small factor business desktops (dc7700 and similar numbers) which are built like tanks and still perfectly usable but similar product may be available from less well known retailers at lower prices.
Depending on what you pick, you *may* want to add more RAM (£20), DVD writer (£20) and a graphics card (£25). But you won't *have* to if your usage doesn't need it.
reduce reuse recycle. you know it makes sense.