We are a family of four - two adults and two preschool DC (one in nappies, so no flushing yet). We are all at home all day, and ever since DC2 was born in 2020 we have consistently averaged just over 310l a day. The two adults shower every day and we bath the kids together two or three times a week.
Your usage does, on first glance, appear profligate although it can't possibly account for anywhere near three times what we use. I agree that you must have a leak somewhere, or are being metered for everyone else's.
Four loads a week on bedlinen and two on towels? We do one for each. Our washing machine uses anywhere between 29l (40 degree eco wash) and 80l (20 degree cotton wash) so it does make a big difference which programmes you use. Unfortunately it's often a trade-off between water and energy use, and I know which is costing us more right now.
Dishwasher on every day? We can usually make it last two. When it was just two adults, pre-kids, we'd easily get three days and often stretch into the fourth. Our dishwasher uses 9l on the eco cycle. Do you wash stuff up in the sink as well? That's another 10l or so there.
What kind of toilet cistern(s) do you have? I read decades ago that about 70% of all domestic water supply is purified to drinking standard then flushed down the bog, and I could believe it with some of the monster mid-20th century or earlier cisterns at 10l or more each per flush. Our dual-flush cisterns use either 3l or 4.5l.
How long are the showers? We're in and out in well under five minutes, but I once lived with someone who thought nothing of spending half an hour in there.
I'm guessing that at the moment you're not watering the garden or filling 500l paddling pools up regularly - the other two massive and increasing demands on water.