ex owes me 30k

I have been living with my ex boyfriend for 2 years. The house is his but for the past 2 years I have paid half the mortgage bills ect.
as my ex has a son we decided to add an extention onto the house in order to give his son a room of his own. my ex could not get a loan so convinced me to take a 20K loan out which part paid for the extention (he put 5k in) and bought him a 9k car.

when I first moved in he was struggling with credit card debt so in order to reduce the rate he again convinced me to transfer some of his debt onto my cards.

in total he has conned me out of over 32k. he always stated that as far as he was concerened the house belonged to both of us and that we would be getting married in the near fututre.

my brother in law was painting the new extention and my ex hurried him into finishing it. 2 days after it was finished he ended our relationship.

what grounds do I have to get my money back?

Although the property is your ex-partner's name you may be able to establish a beneficial interest in the property because you paid for improvements to the property and the mortgage. It is a complicated and therefore expensive area of law so you really need to see a solicitor with a view to negotiating an agreement. The costs involved mean it is in neither party's interest to go to court if it can be avoided.