In short, I'm still using the stock EE router (UK) and the coverage is poor. Using a USB netgear dongle. Signal is poor and not able to run ethernet round the house sadly. Standard load of the system is 3x Laptops, 1 x PC, 4 x smart phones, 2 x music players and thats about it. So dual band 802.11AC would be nice but I would need a PCIe adapter for that (fed up with USB dongles). What would you guys recommend?
I used an Intel PCIE AC wireless adapter for awhile while i was living somewhere where I could not run cat cable. It really wasn't bad, I had good range and a fast connection just keep in mind you need a powerful router that supports dual band AC wireless. The power-line adapters are also good however I don't think they can keep up with dual band speeds, power-line adapters are more for if you are very far from the router or have conditions that dampen signals such as steel/concrete structures. Also consider the power-line adapters if not dropping packets is really critical for you I don't know why you would care but they are more reliable in that aspect. Dual band with the correct conditions and equipment can deliver something like 870mbps no power-line adapter is going to come close you would need cat6 or better to beat the max output of dual band wireless. That said you are unlikely to actually get that kind of throughput with wireless.
As far as what you need the 802.11a/b/g/n/ac standard is fully backwards compatible so the smartphones and music players should hook up fine (they just are not likely to get the full speeds) most new laptops support at-least a/b/g/n which is still fairly fast, good PCIE 802.11a/b/g/n/ac adapters can be had for less then £40 and I know you don't like the USB ones but they are even cheaper then that some of them for around £10.
In short if you upgraded your router, got 1 PCIE adapter for the PC you should be alright otherwise for less money but less speed the power-line adapters are a good way to go.