I googled the Pet Pals service, and they visit the cats for just 20 minutes to feed and clean the litter tray. I personally don't think this is long enough for the cats to feel they have not been abandoned. In a cattery there will be people about for most of the day. When I was doing cat visits, I was there for at least an hour, and would sometimes sit and watch tv with them in the evening.
Also make sure anyone you get is fully insured, as if they leave a window open or not lock a door properly and you got burgled, you would be liable, and not able to claim if they were not insured.