Beneficial interest help

Hi all, I'm new to Wikivorce, it's so lovely to have a platform where people going through separation can find this kind of support and advice.

I split up with my non-married partner 4.5 years ago. We have two children. You'd think I'd be sorted by now, but things evolve...

All the time we were together, he wasn't in the slightest bit ambitious with his business and just did enough to contribute a bit financially to day to day living costs (i.e. bung me some money randomly, usually when he had a cash job and occasionally doing the shopping, but no regular contribution, no bills no council tax etc). I bought a house before we lived together and he, having building skills, worked on it with a labourer. Over that period, I paid the labourer, paid the ex's rent and other bills and gave him some spending money. All the big bills I paid for although he paid for a few minor ones. My loan was about £200K and I spent around £30K for the renovation, when we separated it would have made perhaps £20K profit. We lived there for about 5 years and then moved to a bigger house, however rather than selling I kept the house and rented it out. The house we moved into (where I still am) is owned by my brother's family, we lived here rent free, but after I split with my ex I found I have to pay a tax bill for that privilege, namely I have to count the market rental value as an income and pay tax accordingly. I had to pay a big tax lump for the years we didn't pay as we were unaware of the tax liability at the time.

When we split up he agreed to leave with what he had when we started the relationship. The alternative would have been to sell the house, split the profit (roughly £10K each and from that he would have to pay me back a lump sum I'd loaned his business. Selling the house would have taken away a large chunk of my income and so I said if he wanted it sold he would then have to pay child support. We didn't sell, I wrote off the loan and he paid no support (other than my mobile phone bill). We agreed all this verbally.

With his lack of ambition and me not being there to push him along he let his business dwindle to just ticking along, but he's now earning decent money working with/for someone else. I am hoping to sell the original house and move early next year, but I wondered whether the ex would be entitled to claim a beneficial interest in it; I don't know where he stands on that or whether there is a time limit in England for registering a claim as there is in Scotland? Also, as he now has a decent income, would I be wrong in asking him to contribute towards the children?

Sorry, rather long winded, but I figured it was better to put it all down rather than leaving unanswered questions.