What is reasonable and fair? To buy 'in' or not to buy 'in'?

[BlueAnchor]

Really impartial advice needed hence the impartial bullet points below.

So...Two adults have lived together (not married) for the last 6 years.

• Adult 1 - owns the house, following divorce, pays small mortgage & running costs of house. Equity in the house of £230,000. Has lived in the house for 15 years. Has 2 adult DC's, who lived in the house as children, now at uni.
• Adult 2 - pays food costs and 'treats'; tv packages, holidays, trips out, weekends away. Has 4 adult DC's.

The house is being renovated.
*Adult 1 wants to remortgage in one name, to do the refurb.
*Adult 2 wants to pay for the refurb and be legally entitled to a share of the house (proportionate to contribution)

• The value of the house will increase once refurb is complete.

*Adult 1 is concerned about security and independence; horrible divorce (a long time ago) not sure of jointly owning the house even in small proportions
*Adult 2 wants to feel the house is shared, with joint decisions taken. Adult 2 wants this to be a family house for all DC's and GC's.

• Adult 1 is unsure of adult 2's DC's and their attitudes to money.

Adult 1 and 2 love each other very much and are very happy!

Wow! Happy to answer any questions in return for your thoughts on resolving this.

Greentulips Did your question mean 'why am I paying for the extension when he has 4 children too and should be contributing?'Or more of a general 'why are we extending and refurbishing at all?'

I don't understand why we would downsize? ( not the point of the thread anyway). But, we want a home that our children, partners and grandchildren can visit. We also want a home that suits us, that is modern and up to date; a home that we can enjoy. We both have stressful jobs, so a place to relax.
We are also adding to the value of the house by doing this.

It's was a general 'why extend' when it's mainly just the two of you.

It's a lot of money for visitors!

Good God, don't marry him - you appear to have way more capital and he has more kids than you do.

George no question of marriage. Perfectly happy as I am! Decision not related to finance at all ( tho of course there would be a big impact), just to marriage not meaning anything. I can't see the point...but that's just me!

We are just looking at pensions. His 'Death in service' benefits have been reassigned from his ex wife to me, I have done the same. Legal advice this week to ensure inheritance and right to stay. We haven't decided on the investment into this house yet.