Adding to what Darkseeker said:
1. Yep, SSDs are brilliant so I'd recommend adding one
2. I agree that the GTX970 is excellent, but you'll struggle on a £530 budget to get this card in. A GTX 960 would be great for pretty much all gaming at 1080p (full HD) or below.
3. Ideally yes, but as long as it's a good quality power supply for now, you can always upgrade later. Dual graphics card systems can be very temperamental and I'd only recommend running a single powerful card anyway!
With that said, pcpartpicker have put together a PC of pretty much the spec you want, for exactly the budget (well, a few pence over) you've specified!
Bear in mind (this applies to your build above too), that this does not include an optical drive (Blu-ray or DVD player), and doesn't include the operating system. If you don't have a screen already then expect to put aside upwards of £80 for a nice 1080p one.