p> Firstly the domain was registered at my ISP [...]

The problem here is that you think that your ISP needs to be involved
in this process for some unknown reason. Your ISP is an _Internet
Service Provider_. It provides you with IP connectivity to the rest
of Internet, ensuring that your IP datagrams reach others and others'
IP datagrams reach you. What you are looking for is a _domain name
registrar_, who is a middle-man that will register the IP addresses of
your content DNS servers with a _domain name registry_. Once that is
done, the content DNS servers for the superdomain will publish a
delegation for your domain, pointing to your content DNS servers and
showing everyone's resolving proxy DNS servers where to ask when they
are performing query resolution. Many registries require these middle-
men and won't deal with you directly. Each registry publishes a list
of the registrars that it does business with (i.e. that it has
"accredited"). So go to the registry for the superdomain (For "eu."
that will be EURID, for example.), find its list of registrars, shop
around, pick one that you like, and use it.