Bailey is 7 months old. He is house trained and doesnt actually wee in the house. Although since he learnt to cock his leg about 2 months ago he always cocks his leg up the bin in the kitchen and sprinkles.
He doesnt seem to think he is doing any wrong and up to now I have just cleaned it up and made no fuss.
We have 3 bitches. How can I stop him from doing this I dont like to get angry with the dogs.

What do you use to clean it up?

are there any bitches about also ?

Yes, the OP says there are 3 bitches in the house. If the bitches are in season that will make the marking more likely. I suggest cleaning it thoroughly with the biological cleaners recommended for puppies weeing in houses, and keep an eagle eye on him, so you can tell him 'NO!' as soon as he starts sniffing at it. I always have to watch my boy when we are out at shows, as he has been known to wee on trade stands, me, the ring steward.....!!

I have a 17mth old Rottie I've recently rescued and although he is 'clean' he sprinkles as well.
I use white vinegar mixed with water and that gets rid of the smell. My boy seems to sprinkle wherever one of my other boys have even walked.
All my other dogs are neutered. There are 2 males and one female as well as the Rottie.
The Rottie is entire. I don't want to neuter him as this caused a problem with my other two boys.

I use flash with bleach spray. Thanks Lucy Il try that advice.

Try to avoid using products with bleach for cleaning up wee, because it contains ammonia and, to a dog, smells very similar to wee and encourages them to pee in the same place again. ;)

Better to use a biological laundry solution, then (if a solid surface) give a final wipe over with surgical spirit, white spirit, or diluted vinegar to remove any lingering smell.

I was using a bleach mix when my other dogs were being house trained it was a little old woman in our village that told me that vinegar eliminates the odour whereas bleach just makes it smell more.
I use vinegar now to clean out all the cat/dog bedding and trays.