Can an ex partner (not married) claim for money spent on property both parties rented while they were together?

My GF's ex (they split years ago) is claiming money 'owed' by her from about 4 years ago, as he claims to have spent money on the home they lived in at the time. They rented the place from my GFs father (the owner at the time) and since then they have split up and he has 'sold' the property to his daughter for a nominal sum.

He is clearly more than a little odd and has had an injunction served against him for abusive behaviour. His initial claim was completely out of the blue as a bankruptcy court request! Long story short, it was set aside and he was ordered to pay all costs by the court.

He has also claimed through the county court for the exact same thing (though different amounts!). He is clearly using court forms he can download online as a form of harassment which is really stressing my GF.

For the bankruptcy order, he sent the court and my GF's solicitor completely different 5+ page essays of his interpretation of their relationship full of both hilarious and false ramblings about her character! He signed the original bankruptcy form with an absurd additional pseudonym , an anagram of his own name he also uses in his business, claiming to be both a QC (!) and! CEO of a non-existent company acting on 'his behalf'..

I also suspect he may be defrauding charities, as he runs his business as a registered charity (too new to declare finances) and wants both my GF's 'debt' and all charity contributions to be paid into the same account - his!