Forwarding new domain to PlusNet webspace.

[#1]

Hello,
I've raised this issue with PlusNet but the response made no sense, so I thought I'd ask here to speed up the process. You'll have to excuse any schoolboy errors - maybe things have changed since I was registering domains a few years ago, but this escapes me. Anyway, here's my problem as I asked PlusNet to deal with:
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I've purchased a domain name elsewhere but in order to point the URL to the hosted site (held at Plus.net) it requires a name server.
I am familiar with forwarding and never had trouble before, but the domain registrar won't accept the hosted address (www.hugodrax.plus.com/ggg) and is trying to charge me for DNS hosting. I'm unfamiliar with this concept. It seems an underhand attempt at 'upselling', as the domain is useless as it is.
Is there a 'name server' address I can use to make my new domain forward to the site held at Plus.net?
Alternatively, can I solve the problem by transferring the domain to Plus.net, and using the forwarding function there?
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Any suggestions or clarifications are welcome!
Thanks in advance.

[#2]

If you leave the registration where it is and ask Plusnet to host the domain surely you won't need to do any forwarding?

[#3]

Thanks for your reply.
I suggested transferring the new domain to PN but, apparently, my package doesn't allow domain names, despite having one on account:
'Your current product (Our Extra package) doesn't allow the hosting of domains, we have allowed you to keep current domain (obscura-media.co.uk) but unable to add an additional domains due to account type restrictions.'
I still don't understand what's changed between the tens of domains I bought a few years back and this new one. I would just register a domain, log in to the control panel, then forward it to my webspace. Not any more - the domain registrar wants £9 to 'add DNS' which quadruples the cost of the domain.
I'm still at a loss.