You should reconsider your size since most 27" monitors have a resolution of 1920X1200//1920X1080. Those are exactly the same as a 24" monitors so you get basically a lesser image quality overall since the image is streched to fit the screen.
Considering this, my advice is to either choose the best 24" gaming monitor or go all in and take a 30" monitor (resolution of 2560 X 1600).
Also, what is your budget and are there preferences for certain brands?
I'm not too aware of UK prices I'm afraid. but on with my recomandation :
For the 27 inc market, I would go TN panel unless you wanna pay 700-1000$ :
- Samsung S27A950D : Presents awesome contrast and response times. 120 hz, 3D ready.
- Asus VE278Q (LED) or VE276Q (LCD) : They are great for anything you wanna do