We too have, for many years, had at least one large spider in the house. They occasionally emerge when they make a dash across the floor, most often in the evening. We are quite happy to let them be - we rather suspect there are more than one because apart from not having years of a lifespan, they are not all the same size. Like Lottie, we hava a single name for them all - Spid - not very imaginative but it serves the purpose. I am about to fish one from being trapped in the (empty) bath because it is too shiny for them to crawl out (can't get a grip) so this Spid will go outside into the wider world. That may be a bit of a shock because every part of our house is permanently above 18 degrees. I have always thought that they are all females because, if I am not mistaken, the male is only a fraction of the female's size. Thus Spid is a useful name because it may be taken as gender non-specific.