Whilst I don't necessarily agree with jmg, the whole 'wait for X' thing is always said in these sorts of threads. One can always wait for better, but with the way the pound might be heading it may all be moot anyway. I equally don't think AMD has set a precedent worthy of waiting for any of their lineup to come out when with NVidia already doing some sizeable price drops across their whole range.
But, I would look at the 470/480 at that price point for the larger VRAM however at 4k anything below a 1060 is going to be a bit unless you're upsampling (and in many games that can look far, far worse than a native lower resolution). It sounds like you know this though. I'm just not sure if £150 is going to be any good realistically (even if you wait).
Also if your RAM is clocking low then I hope you took that up with the manufacturer when they were still under warranty. There's something very wrong there, but if it's both sticks then more than likely the motherboard or bios than the memory itself.
But, I would look at the 470/480 at that price point for the larger VRAM however at 4k anything below a 1060 is going to be a bit unless you're upsampling (and in many games that can look far, far worse than a native lower resolution). It sounds like you know this though. I'm just not sure if £150 is going to be any good realistically (even if you wait).
Also if your RAM is clocking low then I hope you took that up with the manufacturer when they were still under warranty. There's something very wrong there, but if it's both sticks then more than likely the motherboard or bios than the memory itself.