Just a little bit more info I've just noticed. I have an Apple Airport Express. This is a small Apple device that connects to my BT home hub and it outputs an analogue audio signal that I can then directly plug into my analogue sound system (it's a way of getting iTunes etc onto an old analogue speaker).
I notice that the light on the front of it is flashing yellow on/off. It should be steady green. I think this is telling me that it has experienced a wifi connection problem at some stage. It does work however, and I can stream to it even though the light is flashing.
Is this this telling me I have a problem with the Home hub? Are the laptop and Airport signalling to me to investigate the Home hub?