as you can with a Bt router or Unifi ap is there any way to combine the 2.4ghz and 5ghz ssids , so only one SSID shows on devices instead of the same SSID twice.
this is for a domestic install and the end-user is elderly so i don't want to cause confusion by them seeing the same SSID twice on phones or laptops etc

Just set the SSIDs on both bands the same.

yes this displays twice on devices with both bands such as my laptop or phone

Hmm - well I've never seen separate networks on the same SSID on any of my devices. Have you unticked "isolate 2.4 and 5GHz bands" ?

no i have not unticked this do i need to.

SSID's are case sensitive, so 'Myssid' on one band but 'myssid' on the other will cause a double listing.
As well as the SSID name, the security settings need to be set the same for the SSID on both bands.
Which model of Draytek router are you using ?