Most monitors do not hit 2560 x 1440 until you hit about 27"
Did a google search on 24" 2560 x 1440 and came back with all 27 In versions..
24" and smaller, that resolution would make for TINY lettering.
About the cheapest are some "Korean" models that use less than A+ graded panels. Was looking at an auria 27 " for $399 USD.
Here is a link to it. http://www.microcenter.com/product/384780/EQ276W_27-Inc...
Might try a search to see if it is available there and pricing.
$400 USD = approx. £260, But have a feeling that if you do find it it would be closer to £400 because of Your VAT.
Just a side comment, The vast majority of the IPS/PSL Monitors Panels come from just two OEMs, LG (For IPS) and Samsung (for PLS).
I'm happy with My Asus PB278Q: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Previous 3 Monitors where Samsung:
One of the Best I've owned - A Samsung 24" 1920 x1200 (Note this is a 16:10 NOT a 16: 9) and Also had a built-in TV tuner
Other two Samsungs, on a 27 In and the other a 32 In, both limited to 1920 x 1080.
The Better Dells are from benQ which are pretty good.
Phillips is not that popular here in the states.
Added: For 30 Inch look for 2560 x 1600 (This is a 16:10 panel). A 30 In 16:10 panel is larger than a 16:9 panel.