Oh this is quite a technical point.
purchase of a house in the name of another - is covered by a 1767 case Dyer v Dyer and there is a presumption that a trust is created basically preserving the rights of the person who has given the money.
however .... in the case of a parent giving money to a child for a house, which isyour case, there is a further presumption that the gift is ouright and without strings. This is called advancement. But if he gave it to both of you, then does the rule apply to you, who are not a child ? Good question
and also the rule can be modified (so it goes back to being a trust again) by a document saying its only a loan.
Hence it is VERY important to see the documents you signed when you bought the house with some of your father in laws money.
In Manchester it is very common for rich daddies to give their daughters money for a house and make sure that they keep a handle on the mun mun. This means that on divorce the rich daddy doesnt give 'his' share to the now divorced husband. Swings and roundabouts. erm and sons too.
I think you are gonna have to wait for the lawyer to come back from hishols