I'm after a very similar answer myself but heres what I've found so far:
This is my first post so allow for some errors but from my hefty reading the views on here seem to say this:
The dell has a lot of problems with firmware and ortho stated on the ocuk website as been the best 24" monitor, gets slated by monitor exsperts and if you want to game useless due to huge amounts of input lag. I've crossed it off my list for this reason.
The HP LP2475w is regarded as one of the best if not the best 24" monitor in this price range with one draw back it uses a wide gamut as apposed to normal gamut which can make images look different in normal web viewing and genral pc use. This seems to be a big debate and a lot of people dont see a problem with it where as others chose not to buy the screen for this reason and went with the hazro. Other benifits are a much better black reproduction and the newest H-IPS screen on the market.
An added note with the HP is the prices are ment to be going up soon according to HP reps.
Very in depth HP review
http://www.tftcentral.co.uk/reviews/hp_lp2475w.htm
The hazro HZ24Wi is also again ment to be one of the best 24" monitors on the market with a slightly better average input lag (i'm going of comments no acctual numbers here) slightly worse black reproduction this is due to the IPS technology. But uses a normal gamut and is regarded as a slightly better all round monitor from people that have had both this and the HP.
Here's an in depth hazro review ortho its the older version of the screen and you need to read abit of the 26" version "i" review for the benifits of the newer model.
http://www.tftcentral.co.uk/reviews/hazro_hz24w.htm
The Hyundai W240D-PVA is ment to be a good screen I can't find much info on this screen but it uses PVA technology which is regarded as slightly lower quality than the better IPS screens.
Thats my little round up would be great if one of the more knowledgable members could do a better one.
But the major question I'm asking myself is, are the price differences worth it? Anyone else care to comment
The Hyundai is £300
The Hazro is £388 (£88 more than the Hyundai)
The HP is this week £435 (£47 more than the Hazro and £135 more than the Hyundai)
Hope thats some help if not abit late it does take a lot of reading to work all that out.
At the moment I'm gonna go with the Hazro due to it been cheaper than the HP and more of an all round screen, but the HP does look tempting. Unless someone turns round says I got it all wrong and for genral use the Hyundai is the best bang for the buck.