For a cheapish option, I agree with the dell suggestions. What is your budget? Decent monitors can go from anywhere between £200 and £4000 and beyond.
Firstly, don't go for a monitor based on a TN panel. They have narrow viewing angles, low colour gamut and have to resort to dithering to up the colours. Ideally you want an IPS based monitor with a colour gamut as close to AdobeRGB as possible (Or even wider if you can).
Secondly, once you have a decent monitor, buy yourself a hardware colour calibrator. It might seem a lot to spend £100 or more on a calibrator, but trust me they are worth it if you are serious about image editing and getting the most out of your display.