Correct way to transfer in .co.uk from 123-reg

[#1]

Hi All
I have a .co.uk domain I'd like to transfer in to a plusnet account. I'd like it completely transferred, not just hosted by plusnet. On the 123-reg site it mentions changing the IPSTAG and the nameservers, but on Plusnet it makes no mention of changing the nameservers unless its hosted only?  I'm keen to get this right so am just after the correct method?
kind regards
rob

[#2]

I'm sure others have a better grasp of this than I have but this is my understanding.
It isn't necessary to change the name servers since the original entries at 123-reg probably become non-authoritative as soon as the IPSTAG change becomes effective. However changing those too in the 123-reg control panel won't do any harm.
Once Plusnet accept the registration their name servers should be authoritative by default. I don't think they permit domain registration without hosting (except through associated companies).
David