I recommend that you consider the 9800x3d which has just been released by AMD since you are buying new. It has unseated the 7800x3d as king of the hill for gaming. The reason why the price of the 7800x3d has gone up and is hard to find is because of the release of the 9800x3d. The 9800x3d retails for $479 in the U.S. (not sure about UK) and if you search in this forum you will find multiple threads that give it positive reviews like this one.
You can also check out this review as to why the 9800x3d would be better than the 7800x3d for gaming.