I just found the spider above in my home. Having carefully looked it up in my Collins guide to spiders I have identified it as Anyphaena accentuata (sorry, no English name for this one!).
Apparently Anyphaena is common enough in the leaves of trees and bushes and is easily identified by the markings on the abdomen that are unlike any other British species of spider.
As a side note, notice the large, swollen palps at the front of the spider indicating that this is an adult male, as the palps of female spiders typically look far more like additional legs than possessing this fat “boxing glove” appearance. This is true with most spiders (even tarantulas) so is interesting to look for whenever you see a spider.