Right, well first of all you need to determine what you want to do with your sound install. Do you want to keep it standard? or do you want to be running a number of subs and components with a set amount of amplifiers.
If you arnt really bothered about your sound install and just want to be able to buy cds, just buy anything you want thats reasonably cheap and looks good.
If you are wanting to run a number of amplifiers (which will run a number of speakers in your car) you need to get a head unit with pre-outs. One set of pre-outs on a head unit is commonly used for subs, and then any other speakers, are ran from the headunit. Running 2 amps, its best to have 2/3 pre-outs, and having 3 or more amplifiers running from your car its best to have 3-pre-outs.
You really need to have a think about what you buy now, and how it will affect you later on, as you dont want to spunk £200 on a cd player that hasnt got the features you may need in the future, which will mean you have to buy yet another head unit later on down the line.
Anyways, the headunit im currently running is an Alpine 7876rb
Originally i had a nakamichi one (slightly out of your price range) which was amazing and had great sound quality and features, although lacked in looks. I then got the alpine one that i currently own, and then owned a Pioneer PH-9600 or sumink like that, which was good, and had more features than the alpine, but lacked in sound quality, and amps did not run as well of it, as the alpine one.
I then reverted back to the Alpine 7876rb for 2 reasons, cheap and also very good. Due to all of the newer ranges coming out, this can be picked up second hand for about £100 (originally cost around £500 new a few years ago)
Spec below:
Silver finish (with blue illumination)
3x4volt pre-outs ( 1 dedicated sub-out)
remote control
4x60w internal amplifier
FM/MW/LW RDS
CD text
CD changer compatible
dimmer control
BBE
Blackout mode
1x aux in
Traffic info
rotary volume knob
Face-off security
Places to buy them are limited i suppose, i dont believe alpine make them anymore, so try Ebay or amazon, i picked up the one of mine for £97 off ebay, and also sold my standard cd player for £107 on there
....so i made a profit, and own a great head unit now.
For your price range, if you can get hold of one, they are a very good head unit! But its upto you.....