Correction to my last answer.
If the builders broke into your house by breaking a door or a lock this is a much more serious criminal offence , it will be classed as breaking and entering.
I think the police probably are confused about exactly what happened , as we were. The police probably think that the builders got in through an open door , which would be Trespass , a civil offence.
If the builders got in by damaging a door or a lock that IS a criminal offence and you need to tell the police that.
I realise English is not your first language and that is causing communication problems. Is their anyone who can act as an interpreter ?
I think that if you go to the Police and tell them you need to report a criminal offence , Breaking and entering, but you can not speak English very well they have to get an interpreter to help you, this will not cost you anything it is up to the police to make certain they are getting the full story and to get an interpreter if nessesary.