I can't think of a way of making it clearer than above. Would this patent for cystic fibrosis susceptible transgenic mice apply in th UK i.e. prevent a similar patent from being granted in the UK?
Actually the title is ambiguous but the body of your question is more specific. You did make it clearer. Patent rights are territorial so no US patent "applies" in the U.K. for purposes of alleging infringement. On the other hand, the U.K. and every other patent office wants to only grant patents for things that are novel on a world-wide basis, particularly in terms of publications and patents. So any journal article, patent, published patent application, etc. on a world wide basis that predates an application "applies" to be used against it. (This is a simplification in that the rules of what can and can't be used vary and can be arcane.)
A quick search did not turn up a UK or EPO counterpart to this patent. Separately, the UK does allow this type of subject matter to be patented but, for example, Canada famously does not.