I have been scammed and will have to do an erase/reinstall to clear it . the problem is I don't know how to save all of my Bt mail to somewhere safe. I have a spare external hard drive and I also use Carbon Cloner for weekly back up to a external hard drive but I don't know if CC will save all my emails.
Presumably you are talking about reinstalling your operating system on your device.
Log onto your BTMail account using a web browser and check to see if all your emails are there. If they are they will be on the BT Servers and will not be affected when you reinstall your operating system.
Once the system has been reinstalled you will be able to access your emails in the same way as you did.
If you are not sure how to do the reinstall I would suggest that you employ the services of somebody who does.
It would be good to have someone reinstall my computer but how can you find someone who can be trusted. I have already been caught out thinking I was dealing with Apple which was not the case.
Find a local computer store or a Currys/PC World store and they should be able to help.
The advice from @gg30340 is spot on, but please change the password on your e-mail account as your scammer might already have access to it.
Wiping your hard drive and re-installing Windows is not difficult. There are plenty of tutorials online, and if you prefer audio-visual learning, there are demonstrations on YouTube.
If it's Windows 10 or 11 that you'll be reinstalling you can do so without losing your documents.