How to feed outdoor cat for days without attracting rats.

Hi, we started feeding what was a very shy juvenile cat a couple of months ago. He's basically leaving in our garden now, staying in a cat house we bought him and he's just so loving and friendly. We are going abroad for 2 weeks over the holidays though and we do not know what to do. A friend can come around every 3 days and we wanted to use a gravity feeder but I am very worried we'll attract rats and foxes (we are in the UK so no racoons). How can we avoid that? Especially the rats, I am so scared that we'll come back to a pest infestation situation or that the cat would have been scared away or bitten. I have been searching for days but can't find a solution. Please help. We want to bring him to the vet when we're back and possibly inside (though we need to check with landlady who was against pets).