I know they're moving premises and are supposed to be re-opening in 2019 but there doesn't seem to be any info on the website (new or old) as to when in 2019 it's likely to be... Hope they're not running behind schedule. EDIT - ANSWER FOUND: OPENING 11 SEPTEMBER 2019!
Answer found! the CRO website now states that
Kresen Kernow, is due to open for public research visits on 11 September 2019.
Kresen Kernow - Cornwall's new archive centre
There will be a public open day on 7 September 2019.