Webserver on lan behind nethserver - https, acme-dns etc

Im looking to access a webserver (using https) using nethserver as the reverse proxy and am failing to get this operational and am going round in circles - letsencrypt is the current issue. i am taking the approach to be that i need to get a wildcard letsencrypt cert for my domain (my webserver is using various subdomains). i have taken the acme-dns module that danb provides as the approach to this but i am failing to setup the requisite dns records on my hosting provider / domain registrar as follows:

ns1.acme.example.com A $EXTERNAL_IP
ns2.acme.example.com A $EXTERNAL_IP
acme.example.com NS ns1.acme.example.com
acme.example.com NS ns2.acme.example.com

the A records are achievable but I cant find a way to setup the NS records. The domain registrar is TSOHOST.COM. Obvious question is if there is a domain registrar i should switch over to? or am i missing something obvious with existing registrar.

thanks for any guidance

ive checked with tsohost and they dont believe delegating authority over a subdomain to an alternate nameserver is something that can be done… so my question can perhaps be put more simply - can someone advise a domain registrar (my domain is a .co.uk) that will allow me to complete the config danb mentions for acme dns… i think this can be summarise as allowing the addition of NS records but im not an expert here!