Joint mortgage after separation help

Newcastle93

I have recently separated from my partner and we have a joint mortgage together. Long story short we only bought the house 2 years ago and I am not yet in a position to buy him out. We have a separation agreement in place and the deeds have been changed so I am 95% and he is 5%. He is insisting on paying 5% of the mortgage payment despite me agreeing to cover 100% as he no longer lives there.
So in short my question is, will this then entitle him to more than the £ value agreed in the separation agreement or not. My original solicitor advised me to not take any money for home improvements, anything that will add value to the house so my question is are mortgage payments taken in to account or irrelevant when it comes to separating the assets upon buy out or selling the house?

Any opinions/help would be greatly appreciated.