To be fair mate, Wolfdog didn't agree with everything that you have said here. Yes, he does say that he believes it could be possible for there to be a breeding population of big cat of some sort in the UK, and that they are indeed very illusive animals.
On the other hand, he mentions that there are Jaguars migrating from Mexico to the US, that are very seldom seen, yet they have been captured on trailcam. Now we are probably talking very few animals, yet there is real evidence.
I have certainly taken something from his post, hopefully you have too.