Ok so I did so more research myself and please correct my assumptions if they are not right:
A full backup does not break log chains (only a log backup or a switch to simple recovery can do this), it will however reset the base backup which would affect any strategy which involves differential backups.
Therefore as you suggested HanShi I could use the WITH COPY_ONLY to make a non interfering full backup.
Each log backup taken after a normal FULL backup has a sequence to this last FULL backup as initial starting point
But provided my log chain is complete - even if I did do a full backup without the COPY_ONLY - surely I could still point to an older full base backup and roll forward remaining logs in the chain...even past the point of the newer full backup?
Thanks