I rebooted the server earlier, not because we were offline,I was working out why I could not get on when the rest of the server was active. I had a DNS issue on my Mac preventing my access. Can't see that that would have affected anybody else.
DNS went down, nothing I could have done about it, fortunately it was only 45 mins or so. What threw me was other shares on my server were working. It transpires the new server is set up with a separate DNS entry for each share.