Most graphics cards will generally be compatible with most builds as long as they have a spare PCI port, room in the case and the right power supply. Nvida recommends 600W minimum for this card, so you a pushing it a little, but it will provably work. It also requires one 8 pin connector and one 6 pin connector. Your PSU only has 6 pin connectors.
TLDR: You need a better power supply. The one you have is only 70% efficient. I recommend the EVGA 750W fully modular PSU. This power supply is 90% efficient and has the right connectors as well as being modular.
Check the size of your case, you are using an mATX case, make sure that the dimensions of your case fit the graphics card (it will, probably)
The 770, a card around the £200 price bracket, is a very good card, it will play games 1080p ultra settings. If you are looking for something cheaper, the R9 280x is a viable option, and for a bit more the R9 290 is certainly a great card.