3570k overclcok board

It depends on how much you want to spend on a mother board.
Asrock extreme 4 boards are ok, and are priced ok, asus, or gigabyte may be worth a look. About a 550w to a 650w PSU just in case, good quality known brand dont skimp on the Psu.

Any decent Z77 board would be fine. 4.4Ghz isnt a massive overclock, would only require a small bump in voltage (unless your lucky and get a good quality chip) to keep stable.

The normal boards to get for a gaming machine are (in order of personal preference).
AsRock Z77 Extreme4
Gigabyte GA-Z77X-D3H
ASUS P8-Z77-V LK

I'm looking to spend £70-£80, but I might be able to spend a little more if it's REALLY worth it, but certainly no more than £100.

Also, is the PSU really that important, I mean, I get that it is pretty damn important to axctually running the computer, but does a more expensive one make a big improvment over an older/cheaper one? Because I'm confident my PSU can cope with what I want, I've check on a cpuple of those PSU calculators, and I don't really have the moneys to spend on a new PSU, so if I got a new one I'd have to skimp on other components.

Your card has a max tdp of around 180, you wont need a huge power supply, but you should def look into a quality psu. XFX, corsair, seasonic just to name a few. All three of these brands have a psu that could meet your budget and perform well with your components.

Oh, just wanted to clarify, the budget is for Mobo alone, I haven't budgeted at all for a new PSU, since I didn't intend to buy one  

I thik I have it down to 2: the AsRock Z77 Extreme4 and the Gigabyte GA-Z77X-D3H, which of these would be best for my needs? Also, the AsRock seems to be a tenner or so more expensive, even if it is better, is it worth the extra?

Im using an Asrock pro 4 with an i5 3570k and its a fantastic board, you cant xfire or sli but its an easy board to overclock with for sure.