The 1050ti is a solid card. Depending on the games you play it should be more than enough unless you are trying to 4k and max out games like Witcher, Skryim, etc. Your 1000 pound build gets you a ton more than you think. Now I am looking at North American builds and converting money, but at...
£887 you get this: https://uk.pcpartpicker.com/list/BXfXP3 . I would put your 1050ti in there until you want to buy an upgrade. You could go slightly over at about 1100 and get a 1060/1070. (I am sorry, I put Noctua fans in there and I know some people hate them because they only come in brown, but I use 3 of them and they are silent and wonderful)
If you keep your current build, I agree with Phil that I would change the memory and then sit on your hands for a little bit. Your memory needs directly reflect the modeling and graphic design aspect. What games do you actually play?