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Hi, thanks to all who replied to my question. After lurking about the house (!) I have established that he is spraying, and not peeing. The vinegar/water has worked quite well in the areas that have ceramic tiles - thanks for that. Any ideas about how to shift a lingering aroma from wood would be gratefully received (wood laminate - the wee has leaked between the skirting and the floor)
I'm fairly sure the problem is other cats in the district, but I don't know what I can do about them. I shut my cat in at night, and we have 6ft fences, but they climb over sometimes. My cat does go out and seems ok with that - he just really hates other cats