Hi, @gareth!
Do you have any success so far?
It looks like I’m facing a pretty similar issue.
The difference is I run couchbase in a docker container and try to reach it from host. I’m trying to follow that advice Make the ports 8092, 8093, 8094 and 8095 configurable to be able to use docker's random ports - #3 by Arnaud_Villevieille
And my logs (for java sdk client and sdk doctor) look like yours.
I would be grateful if you could share any information.