An unusual thing to find scampering across the arm of the sofa: a Nursery web spider, easily identified by its slender proportions and pale stripe down the centre of the head. I see these amongst long grasses in the great outdoors but I've never seen one in the house before. Note that it's in he bottom of a pint glass in the shot above and not as big and scary as it might seem.

It's so called because it spins a big tent of silk for its youngsters to protect them in their first days after hatching. It's a hunter that simply waits for prey then chases and overpowers it, so perhaps it had to find another use for its web spinning abilities.