for the price it is not a bad option but i would rather go for r9 290 whitch have aged WAY better and wil give alot better fps than 770 but it is power hungry so you will net a decent psu.
That depends on which 770 you get since you have a 2gb and 4gb variant. The 2GB variant would be a huge drawback but the 4GB still is quite usable and runs around the same FPS as a 1050 TI but with much more power usage and heat. To get something faster you would have to look at a used 970 GTX/RX 470 which would be around £55 to £65.
for the price it is not a bad option but i would rather go for r9 290 whitch have aged WAY better and wil give alot better fps than 770 but it is power hungry so you will net a decent psu.