Messages won't sync, cannot delete them from iCloud

I have a bunch of messages in the cloud. I would like to delete them, however it has not been possible to do this.

Several weeks ago I made the mistake of enabling iCloud messages. In theory this would have allowed me to have all my messages on all my apple devices. Except it doesn't work properly. Messages don't sync or sync out of order. Anyway, I decided I didn't want to use a broken feature, so I wanted to ask if anyone knew how to delete the messages from the cloud?

Basically, it says on iCloud.com and on my devices, I have over 700Mb of messages in the cloud, but these messages do not appear on any of my devices. I have tried the disable and delete option on my iPhone, but just get an error message that iCloud settings could not be updated at this time. I attempted this on my Mac and nothing happens if you click the button. I have tried logging out of all devices, completely resetting my iPhone and then logging into iCloud and turning on messages in the cloud, the system syncs, I delete any messages that appear, yet still 700Mb is still being taken in the cloud. I have toggled the keychain option as other threads suggested this, but no luck. I have tried creating new messages and these sync, and then delete these messages, but still 700Mb is taken in the cloud.

Before I use the nuclear option of deleting my Apple ID and throwing my Apple devices into the skip, I wondering if anyone could help with any suggestions?

Thanks.