Let me take a look at this and I'll get back to you in a bit.
You might refer to the notes here and here as part of this answer.
Transfers of assets between the parties to a marriage or a civil partnership are treated as taking place on a "no gain, no loss" basis so long as the couple are living together or the transfer takes place in the tax year of separation.
Since you have never lived in the property in question, the only relief that you are entitled to is the annual CGT exemption which covers the first £11,100 of gains you make in a tax year. As you are still "connected" to your husband for tax purposes, the disposal by you of your share of the house to him will be deemed to have taken place at the open market value. I suspect that he will pay you the market value of your share in any event.
Assuming that your share of the property is worth more than the sum of your share of the original purchase price and your share of the cost of renovations carried out, you will have a gain. If that is more than £11,100, you will pay CGT on the excess at 18% or 28% or a combination of the two rates depending on the level op your income in the tax year that the gain is made.
No more than £32,000 of the gain can be taxed at 18%. That figure will reduce by £1 for every £1 of income you have in excess of £11,000 in the tax year of the gain with each excess £1 being taxed at 28%, the higher CGT rate.
I hope this helps but let me know if you have any further questions.
Assuing that the £120,000 is not conditional, you will be treated as disposing of your share for full consideration at the time contracts are exchanged at the market value of that share at that time. You can apply to HMRC to pay the tax in instalments if you wish since you won't be receiving the payout in one instalment. Your gain would be £70,000 in this case.
You will be treated as having received market value for your share if the disposal occurs pre-divorce. For a disposal post-divorce, you will be treated as having received whatever price is agreed between you.