Thanks everyone for all your help - much appreciated. However still having problem.
Time is sync’d and DNS settings ok (can resolve names, ping etc).
Don’t use multiple nics on DC.
Server attempts to send policy and script files to staging folders in SYSVOL folder but unable to move files out into final location. Agree could be permission settings on SYSVOL folders, if so what should they be?
If delete connection objects for replication, servers do in fact recreate correctly suggesting AD working ok.
Yes, Matt, I am from sunny Hillingdon.
Badger