joint owners freehold each lease part of building

[jonD]

What CGT is due if joint owners of a freehold grant a new lease to each individually for part of a residential building.

Example
2002 purchase cost freehold consisting of 210m2 3 floors paid 210k
joint names simple freehold

2017 create two 999 year leaseholds or share of freehold plus lease, peppercorn rent, 70m2, one floor each
one for each freeholder

market value each lease say 300k each
money changing hands zero

Is there CGT payable or not?

If CGT is payable I am guessing it would be on 300-70 = 230k

If each freeholder has occupied one floor as their main residence does that change?

And the same question applies to stamp duty I suppose.

Is there any way to minimise any tax payable. No money will be changing hands so any tax will need to be paid from savings.

TIA

[jonD]

Hmmm maybe I made the example too complex/unusual [bad habit].

Anyone have any idea on this example.

Unmarried couple buy freehold house in 2000 for 200k.
Seperate around 2008 but each continue to live in house which is changed internally to have seperate self contained parts.
In 2016, create two new leaseholds/share of freehold so that each former joint owner has a leasehold on 50% of building.

How will hmrc look at that:
A.
Each leashold created from 50% of freehold. Current [ridiculous but realistic market] value is 300k
New owner of leasehold is buying 50% from himself and 50% from other owner and the part he is "buying from himself " can be disregarded.
So for CGT he is paying 150k to other owner for something that owner bought for 50k. Taxable gain is 100k

B.
New leaseholder used to own 50% of building. Now has lease + share of freehold for 50% of building.
There has been no disposal so no capital gain.

C.
Some other way.

I guess this is the first question and an answer to that will allow the standard rules about primary residence / part rented etc to be applied.
I have read half the CGT manual but it's not helping / am not finding answers so far.

[Having answered that one in the real world there will be added complexities of part primary residence some proportion of years and % space/value not being 50%. ]

Also just to add this is a planned transaction not one that has been done so please don't shout at me for not having got it right in the first place. Exactly how the transaction is done is therefore not fixed, we will certainly look to sort it with minimum tax to pay since any tax will be paid from savings accounts.