Re-register your car...?

Im considering selling what I believe is a Belfast plate to someone who sees a personal significance in it that I ido not... WLZ 767
The governments site isnt that forthcoming in the immediate sense and i could be reading around the whole subject before getting to the substance of what I want to know- so my questions are.... :)

Presumably I will need to apply to the DVLA for the car to be given a new number ( or even the old number it was first registered with, if they do such a thing ? ) ?
Will the car be allocated an age appropriate registration by default ?
Does it need a current MOT and Tax status to be allocated a number ?
Is it a relatively straightforward process and voila..?
Am I right in thinking its about £55 plus the cost of the new plates once the number has been allocated...?

Does anyone have a minimum sum in mind before the hassle is worth it ?

Thanks for reading !
Think it's £80 for the transfer, you get age-related on change, doubt you'd get the original plate, unlike in Ireland where if I go back with car I'll get 06-WD-3 back which is a pretty cool Irish reg. (you can't transfer them), given normal Irish plates are like 15-D-12345.

Mines now on NI plates, KXZ4221, but I have S555SVK to put on (my initials) but I kind of like the NI plate for no particular reason.
I would agree it’s an £80 fee to put the plate on a retention certificate so you can sell it, the fee includes putting it on the other car when the time comes.
When ever I have removed a private plate (including NI plates) the original number get allocated back to the car.
Pretty cool. That's the 3rd car registered in Waterford in 2006; shame you missed 06-WD-1 ;)
Well it was owned by Robert Finnegan, the head honcho at Three Ireland, guess he chose the 3 to reflect his position.

I don't know for sure but I believe you can pay extra to reserve the early number plates in Ireland to NDLS or whoever does it, that's the only path to a private (ish) plate in the Republic.

There's a pic when I blu-tacked the IE plate back on in UK for reason. Not the full IE experience tho, you have to show the NCT (MOT), Insurance and another thing I forgot (reg doc I think) in the windscreen, takes loads of space. Nice in UK now, nothing stuck on windscreen at all, I hate that, even the main dealer sticker bottom rear window, hate that too! And on numberplates! IMG_0299.JPG