fionajk52 - we are presently in a very similar position. The couple have been together for 10 years and are not married. Two years ago we provided the deposit on the understanding that if at any time it was possible to repay the deposit, it would be done. The house is now sold and the other party is saying we are not being repaid 'her share' of the deposit. Neither she, nor her family, put anything towards the deposit.
The Mortgage company asked us to sign that the money was a gift. This was the only way it would be accepted as the deposit. We signed that it was a gift. So, legally it was a gift but morally it was a different matter. In two years she has benefitted from the half deposit plus half equity. Also, our son paid the mortgage, loans, childcare and all utility bills. She bought the groceries.
The house has made equity but even so, she is still keeping 'her half of the deposit.'
She is legally correct. Fortunately the sum of money concerned wasn't as great as your £60k.
There is a thread on here about it. I felt utterly betrayed but have come to accept that like yourself, we have to wave goodbye to the money.
I'm sorry this has happened to you.