I think the main thing is you are leaving him in his own home, much better for him , he will be fine and knowing the neighbour will be alot better than a stranger.He will probably laze about .But expect him to ignore you when you come back [ mine do] it's only to show you that he could not car less lol.Have a nice holiday and don't worry, he will be fine.I would say that the catflap should be locked at night,to stop any strange cat from entering as that could well upset your cat.g.