"However, as there are children, in most cases this would not be enforced until the youngest child reached 18 - assuming you would be the resident parent, you would probably have the right to live in the house in any case until then - which would give you time to make arrangements to buy him out." That's not strictly true either - in fact mesher orders are increasingly more difficult to obtain now and generally solicitors are reluctant to go down that route.
It is also bearing in mind that:
A mesher order will tie you financially to each other for a considerably longer time (child maintanence aside) than you would necessarily desire)
If the rp is reliant on the ex for financial contribution to the mortgage it means that it puts him in a position where he potentially cannot move on and potentially even in a position where he has to live in accommodation which may not be as suitable for his children than otherwise would have been the case. While people might argue that he should be financially responsible for his children's home, everyone does have the right to move on after a divorce, and it is not fair that one party should have to pay the penalty just because the other feels they should have a right to live in that particular house.
Finally you need to bear in mind that the financial settlement on the sale will be dependent on the house price at the time of the sale, not at the time the order is granted. So if your house is currently worth £300k with £50k of equity and house prices increase by 200K in the next eighteen years he will be getting £150k as opposed to 25, or if you decide to buy him out you will need to raise significantly more in order to be able to do so iyswim. Similarly if prices drop you will take the financial hit for that as well.
And if you are the lower earner you need to be careful not to take on a house that you potentially can't afford. MPeople told me I should push to stay in our house when we got divorced but I opted not to and my xh bought me out. Since then he has had no end of structural and internal problems with the house which could never have been foreseen, and which I could never have afforded to rectify if I'd ended up staying there.