Help! Cat coming in my house 😩

Someone in my street has a tabby cat that keeps coming into my house.

He looks well cared for, nice coat, not under/overweight, has a collar etc (no address tag as far as I can see) so i know he’s 100% not a stray.

He’s been breaking into our kitchen through the cat flap for about 12 months but we can never catch him or stop him 😩 our cats don’t have collars so as soon as we hear him we have a cup of water on the counter that we try and throw to deter him but he’s always out the flap and gone by time we get near him, he hears us get up.

We recently had our old door blocked up and moved the cat flap to some glass doors about 12ft away - my own two cats took 2-3 days to work it out - he figured it out the first night! I was soo hoping moving the flap might stop him but no.

We ensure the bowls are moved once ours are fed to try and keep food out of the equation.

Last night we accidentally left a (sealed!) pack of wraps on the counter and we’re pretty sure he’s been at them because in 5 years my own have never gone for food we’ve left out. The packet was ripped to shreds.

My OH isn’t a cat person, he quietly tolerates the two we have because he knows I love them but I 100% agree with him that we don’t want someone else’s cat coming in our house and need to stop him. Clean though he looks we don’t know his vaccination/flea/worming status and we have a toddler and a another baby on the way.

My partner blew this morning after the cat had quite likely jumped the counter and said “that’s it now, cat flap is locked at night and no cats come in at all”. We can’t keep ours in because the younger of the two gets highly stressed and even with access to a tray will pee beside it and equally I don’t want to penalise ours by locking them out either when they aren’t doing anything wrong 😫

Any tips on what I can do? I contemplated knocking doors to see who’s cat it could be but I know if someone knocked my door I’d be just as stuck on what I could do if it was one of mine and would only be able to suggest throwing water at them to deter them.

Edit to add: the last cat flap in the wood door was a chip reader one, but for some reason my cats chips seem to relocate/migrate (happened to my cat that passed before I had these guys and one of the ones I have now) and they were also difficult to train with it so we turned the chip reader setting off and settled on a standard cat flap for the glass door because the old one had been used as a standard flap so it felt like a huge waste of money 😩