Thank you Slartarama I will bookmark these pages and try tomorrow, as I've just got back from watching Blyth Spartans play Blackburn and have to be up at 4.45 am for work and I've been here before ended up not even getting to bed thanks to starting something that looked simple and ended up getting personal between me and the equipment involved.
The strange thing is, it used to work better than it does now! I'm sure I had two way networking at the beginning and I definitely know the laptop was picked up by the mac's wireless connection. Could I be causing problem having both the ethernet and wireless networking active on the mac?
Another thing I could try is boot into the other OS, Windows XP and see if that works both ways - in fact I don't know why I haven't done that before
Many thanks for your continued help and I'll let you know how I get on tomorrow night.