HI, I have a situation where a friends and I have been house

HI,
I have a situation where a friends and I have been house sitting for another friend who has been working in Iraq/Iran for the last 3 months, we had a verbal agreement where we would contribute towards bills and look after the property whilst he was away in leui of paying rent. On his return (2 weeks earlier than agreed) he informed us we had to move our stuff to the house by this weekend which we agreed and agreed to give him 200£ in cash on our leaving.
When I went to collect my things yesterday he refused me access to the building claiming i owe for a parking ticket at the sum of 500£ which I had to pay before removing my things from the property. I agreed to pay straight away via bank transfer on receipt of proof of the bill - this was refused by him to me saying he doesnt need proof and that he needs cash as his bank account have been frozen, at this point he strated becoming aggressive and threatened me so I called the poilce, The police attended the propertY, mediated and negotiated the return of my goods on the Sunday morning at 11am. At 10.30 am i received a message to say i couldn't collect my things and to contact my solicitor.
I have a large amount of personal data on various laptops and hard drives in the building along with part of my driving licence and all my financial information, my birth certificates as well as my work laptop (i work for a educational institution and may have sensitive data opn my work laptop)
I was wondering if there is anything I can do and if I can report this as theft as he is refusing to return my goods (they are locked in his house and he is knowingly holding them without reason)
Many thanks in advance