I live in the middle east, these insects seem to come up the drain. I find them mainly in the bath, occasionally in the toilet and sink. Never in the bidet-which is never used so assuming its always dry. We rent and monthly pest control sprays makes no difference, the management think they are ants or termites.
They are UK based but are full of experts who will no doubt jump at the chance to identify them for you. I'd suggest trying to give clearer pictures when posting on that forum though, and giving details e.g. size in mm, how many legs, any other colourings you see on rather than black