Hi there, in and of its self a 1080p 27in monitor should be fine for gaming. The pixels are bigger than in a 1080p 24in but (depending on your eyesight) a 27in at the same resolution will still look good, though slightly less sharp.
The big issue is really that the cheap ~£200 27in monitor are using TN type panels. These are cheap TFT panels that offer good responsiveness and low input lag - so good for gaming. Though they have the downsides of tight viewing angles (if you move your head from looking dead-centre the colours shift and there is colour banding at the extremes of the monitor) and not great colour accuracy. Because of the viewing angle issue I wouldn't personally recommend a TN panel as big as a 27in (hence why you never see any 30in+ TVs using TV panels) - though you may find the issues and colour banding/shifting less annoying than I do or learn to live with it.
Also, from personal experience I went from a Dell 2408WFP 24in monitor to a 27in 2709W and I found the difference in size to be really quite striking. I find the experience of using it much more immersive than the 24in and it is nice that text is a bit bigger at the standard size - so stuff is easier to read. Though I must highlight that both of these Dell monitors use 1920x1200 resolution S-PVA type panels - so my reservations on 27in TN panel monitors don't apply to these.
Also, in terms of prices the comparable 24in 1080p TN panel monitors are actually quite a bit cheaper than these 27in versions - for example
this perfectly good 24in 1080p TN monitor currently costs £150.
If you are looking for a higher quality monitor for around the budget of the 27in TN monitors then I would have a look at
this 24in Dell U2412M. This monitor uses a higher quality E-IPS type panel (which offers much better viewing angles and colour accuracy at the expense of some responsiveness) and is also higher resolution at 1920x1200,
here is an in depth review if you are interested.
Also, as highlighted by The Baron, if you are looking at the Hazro 27in monitors then you not only get the large size but also a high 2560x1440 resolution and high quality H-IPS panel. If you can afford it, one of these monitors would be VERY nice to have (the resolution is so high that pixels are actually smaller than a 24in 1080p monitor - so really nice sharpness), though also bear in mind that if you plan to game then you need a beefy graphics card to run games well at such a high resolution.
