Hi Unfortunately I don't have access to the computers there right now, but I'm sure the logs were not showing anything blocked. That is why I was having problems.
Even with an "any source to any destination - Pass - always" rule in place, it (the firewall) was still blocking the file and printer sharing (SMB) traffic this did not show in the logs and was only evident when the firewall was switched back off - everything sprang back to life then.
Same story for all the network computers at the site and unfortunately I don't have another avast installed site against which, I can compare this with.
Surely an "any-any-pass-always" rule will pass any traffic from any machine to any machine always....?
Colour me confused!
JB