I have had the "CallMinder" service for 25 plus years. On my recent bills I just noticed they call it something else. It looks like from the helpful recent posts above that the list for the superior "Voicemail" rather than inferior essential service none of those enhancements in my case are needed so "essentials" is the one for me. Unfortunately the list says nothing about personal recorded messages so it sounds like if I want to keep the one feature I find useful - the personalised message I can have that with the basic essentials so could save the £4 a month I pay once I am moved to Digital Voice.
Once I am moved to Digital Voice I will check how the pre existing recorded message etc is working or not and then I suspect I will have to call BT to remove voicemail and move to essentials voicemail and save the £4.
As ever I find the forum very useful so thanks for all the answers.
According to this site, you do not need enhanced voicemail to record your own message.
https://www.bt.com/help/landline/all-about-voicemail-for-digital-voice-
Perfect, thanks. I will migrate to DV later this year and once I am sure the internet and landlines are working then move on to tackle any voicemail issues.