Letting agent not passing on tenant's rent to landlord

Letting Agents

The letting agent who manages our HMOs owes us a lot of money in rent that he has collected, but hasn't passed this on to us. He tells us that all the tenants are up to date with their rent, but there are large gaps between his transfers to us, i.e. after months of no payments and no statements, we receive a statement dated August, but the tenants payments on the statement are only up to Feb, April and June respectively - none are up to the date on the statement. We have written to him asking him to pay us the rent he owes, but he just comes up with excuses. We have tried to help him by compiling a spreadsheet with the entries from all the statements he has sent us to date and we have reconciled all statements with the money we have received in the bank account, so we know that the spreadsheet is correct. We also know that the tenants are still resident as we have been to the properties to check this. However, despite presenting him with all of this proof he is still in denial, but unable or willing to prove anything otherwise. I have tried the PRS, but found out that he was expelled. I found a couple of worrying reviews on google suggesting the same experience for another landlord. When I advised him of my findings, he tried to make excuses and said he didn't know anything about the reviews and that it was a mis-understanding with the PRS. We have been back and forth since July and he has made a couple of token payments, but no statements and it doesn't look like he is going to send them as this will add more weight to our claims. Where do I go from here. I am reluctant to change agent until this has been sorted out