Yes, I have downloaded the new version , yes I have got a new serial number, but no, it will not accept it ! Maybe it was just a glitch in the database or something, I will try again when I get home tonight. Thanks anyway.
Edit.... I have just read a new comment on the main SU 2018 thread, you have to click on the send email button to also get a new authorization number, not just the new serial number generated online. Perhaps not the most intuitive way of updating software for new users ? Anyway, something to do tonight......

OK, so a few weeks ago I bought SU Pro, with the maintenance and upgrade full license and now they bring out SU 2018, which I am apparently entitled to upgrade to.
In Sketchup 2017 I "check for updates' and it tells me my version is up to date ! I cannot see any link to update at sketchup.com, only to download the full version of SU 2018. I tried doing that but it will not accept my serial number/authorisation code ( I checked my license and it has been changed to a newer serial number from SA-xxxx... to TA-xxxx.., I've tried old and new !)
So, in plain language please, just how do you update from to 2017 to 2018 ??