Pointing Plusnet registered website to 1&1 servers

[#1]

A bit of background
I have a free domain hosted with Plusnet (from the security breach years ago) and I have a basic account with 1&1 for another website which includes hosting unlimited external domains.
Rather then moving the registration of the domain to 1&1 (costs £2.99 per year - I am a mean sod) I thought of hosting the domain at 1&1 which is free but leaving the registration with Plusnet.
This means that I can set up a separate set of email addresses with 1&1 then progressively get my contacts to change to the new address and, should I decide to leave Plusnet broadband, I can do it with no disruption to my main emails
What are the steps I need to take to do this.
Is it something I do via 1&1 or via Plusnet

[#2]

Hi Jim,
I think the short answer would be 'both'. I don't know the details at the 1&1 end, but you would need to set up both hosting and DNS for the domain with them, then you would need to ask Plusnet to change the nameservers for the domain to whatever they are for 1&1. Alternatively, you could set up hosting on 1&1, but leave the DNS with Plusnet for now and just point the A and MX records for the domain at the 1&1 servers, using the domain config form in your account. Sorry if that's a bit sketchy, but I've not been through the process with these hosts.
Gabe

[#3]

Raise a ticket and ask Plusnet to change the DNS servers to 1&1.
There is no need to change the IPS tag, unless Plusnet are unwilling to change the DNS servers for you, then you do need to move the registrar.
You may even be able to do this through the domain control panel in the portal ... it's been a while since I had a domain with f9.