Thanks All - I think I get it.

I am happy to spend a little extra on a Switch over a hub ( in fact some of the switches appear cheaper than Hub's for some reason ?? ), as

a) have two long runs of cable down to the garage servers, that I notice a speed issue with ( this may be a bad cable or low spec PC's though )

b) I could do with the speed when moving loads of MP3's ( to Empeg etc ) and I have a large collection of videos that I need to stream to the TV PC.

Guess I missed something on the speed front though, I already have the Netgear 8 port Hub mentioned, as Dell Receivers and Empeg's need 10mbit. But does a Switch work the same way as a Hub in that it does NOT reduce the speed down to 10mbit for two 100mbit devices that are file sharing etc.