Are these fears of 'tradespeople' using toilets limited to men? If the surveyor was a woman, would you (even lightheartedly) be questioning her ability to use a toilet in an appropriate manner?
And, would the thought cross your mind that she might be a Mumsnetter, and is the toilet clean enough for her? What if she judges you
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Anyway, I'm sure a lot of the 'fear of strange man using my toilet' wouldn't exist if you all had toilet brushes like normal people
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Oh dear, I really need a shit, I wonder if she'll mind if I go, or can I hold it until lunchtime when I can pop out to McDonalds.
Damn, I really need to go, I'll just ask Mrs Mumsnetter if she minds
Oh, yes Mr Surveyor, of course you can.
Oh that's better. Then Oh no, it hasn't flushed, quick, where's the bog brush!!!!! 
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