14.04LTS upgrade to 16.04LTS fail to resolve upgrade

Hi, can anyone clear up some confusion over this upgrade?

I am ruing 14.04LTS and trying to upgrade to 16.04LTS released today. I read on Canonical website and elsewhere that LTS versions can be upgraded, from one to the next, directly through Update Manager.

However the 16.04LTS is not being offered as a system upgrade in my Update Manger.

Searching the web I get some conflicting information.

I read on one site that the new LTS will not be offered to existing 14.04LTS users until July????????

The Canonical site does not mention that it is not possible to upgrade directly from 14.04LTS until July.

Then I read on another site that it is possible to upgrade from 14.04LTS using $ sudo update-manager -d as a development upgrade.

I Have tried this and the 16.04LTS is then shown as available in Update Manager.

Upon installation the first step is passed OK but it then fails on the second step while checking packages.
I receive an error window and a message saying the update failed to resolve due to one of several factors including ruing a development version or other unsupported software (which I am not)

Any ideas for a fix, any suggestions, or will I have to wait until July?

Thanks

Nigel.