...OK i've now found out that:-
my PC, via my router/ISP (Tiscali) - errors
a laptop, via my router/ISP - errors
son's PC, via my router (wireless), via my ISP - errors
another admin, via his router, via his ISP (not Tiscali) - AOK
tomorrow i'll try laptop from another location/another ISP.
Recently upgraded to 2Mb from 1Mb B/B - is there any way this might have caused the problems ?
Could the problem be with Tiscali ?
or, my D-Link Wireless Router ?