Please don't assume all a screen has to be in order to be good, is IPS
If yours is actually faulty, it will be better than what you have perhaps. I've used other AOC screens before. A couple have been OK.... by which I mean OK.. not good, or great.. but OK... I've not actually used this one, but have used the 23" version. It barely achieves sRGB gamut, and needs the backlight set to almost 0 to set it to the accepted standard of 120cd/m2, which means that blacks are crushed together, so fine shadow detail will be terrible. Once calibrated, best it could manage was a 390:1 contrast ratio due to this.
This all indicated that the panel and circuitry that drives it was designed for televisions, not monitors. A common ploy for Chinese manufacturers, as it saves money, and people who don't know any better think they have a nice computer monitor for a bargain price, when in reality they are getting a cheap 21" television, with half it's insides missing for a rather extortionate price. The one linked to above will be crap, and it's 23" sibling.... is crap.
There'll be tons of people out there who will tell you they're great... but they're just consumers who have no idea what a great monitor looks like so they just think it's great.. "oooh... it's as good as my tele"

. There are also people out there who will tell you that a Citroen C1 is a great car. It is not a great car.... it's crap, and this is not a great monitor. It's crap. It will be OK for Mr Average to browse the web, watch iPlayer or do day to day stuff... but you seem to be a professional photographer (I think.. you mentioned clients so I'm assuming you are), so why are you messing about here? If you're that skint... then save some cash first instead of scraping the bottom of the barrel like this.
Because of all the above, there's a very real possibility it won't even calibrate, as I had trouble with the 23" version. The blacks are just too crushed when the back-lighting is reduced to a non-retina burning brightness, so you'll have wasted the money on your calibrator too.
Does that mean your monitor budget is £100?... or £200? If it's £100.. forget it. You may be able to buy one that's not faulty like the one you have now, but you'll not get a decent monitor for £100. It's difficult with £200. You'll get a perfectly OK monitor for £200.
Much less than £200 however, and all you'll be getting is a cheapo stop gap monitor. There's genuinely not much worth buying for this kind of money if you want an accurate, calibrated screen.
There's only really one sensible choice, and that's the
Dell U2412. For less than £200 if you shop around, It's a proper 16:10 panel, not a 16:9 panel, calibrates well, and a great screen in every respect. Turn off dynamic contrast if you get one though... it's horrible, and anything
"auto" should be
OFF if you calibrate a sceen. The one thing that lets almost all monitors of this price range down though is the panels are nearly always 6bit +AFRC dithering... which basically means it isn't truly 24 million colours like a true 8 bit panel. You'll need to spend a great deal more to get a genuine 8bit panel and true 16 million colours however.
Ok.. before you run off to spend your money, are you familiar with the whole concept of working in a colour managed workflow? You OK with embedding colour profiles to images, and how to set up Photoshop correctly? You understand the limitations of digital images on non-colour profiled devices, and what the impacts of that are? Do you know how to best mitigate for this? Calibrating your screen is a good idea, but it doesn't mean everything you produce will be bomb-proof. You can still make all the rookie mistakes like embed Adobe RGB1998 because it's "better" and then wonder why your clients are saying the images look washed out on their TV.
BTW.. don't get the Spyder4 Express if you were thinking about it. Crap software, and only single display capable, and is only calibrates to D65 (6500K 0 2.2 gamma) which is fine right now.... as that's what you want, but later, you may want more flexibility. It also only generates ICC v2 profiles and isn't v4 capable. AGain... not an issue right now, but later computer OSs may well drop V2 as a standard, and you'll be left without any calibration.
Get the 4 Pro or higher... should still bes less than £100.