Thanks for your help.
I compared my samba.conf file with yours and I had a lot more settings in global, so I commented them out, and I still had no luck. I then tried messing around with SELinux, and couldn't get anyway- but then found that if I disabled SELinux, I could now get in from my windows machine! (Also added security = SHARE to global)
So all was running fine, so I started fiddling with setting up calenders and mail etc for users, (and I'm pretty sure I didn't change anything to do with samba) but now, I'm getting xp machines trying to connect as guest again!!
(Sorry it took a while to reply)