Have just sent an e-mail to GW web adminstrators to do something about this kitchen spam, e.g. put a spam filter in. Whether it will do any good is in the stars, here's hoping!
Diluted Jeyes Fluid apparently gets rid of cats, maybe pouring some of that down the holes will work as well!
Could it be stone martens? We had stone martens who used to go mad in the garden at night and literally crash their way through the plants crushing everything. They are a real pest here and particularly like to chew cables and rubber fittings under car bonnets, in fact car insurance covers marten damage.
Well, it might not harm anything, but could certainly attract ants! Just my thoughts, if it was me wouldn't do it (except plain mineral water, use that on my houseplants occasionally).
35°C in the shade expected by lunchtime, 32 right now (10am) (wipe sweaty brow smiley!).
Are you puttung cooked food into the compost heap? This will attract rats!
It's not called catnip for nothing! If you don't like "vermin", don't plant catnip!