My understanding is the Openrent advice is not to hand over keys till 1st month’s rent and deposit paid. Ask them.
As he hasn’t paid by move in day he is already in breach of the contract. Seems quite likely he won’t produce the funds on Monday either
I would contact Openrent but best will likely be to initiate the end of the tenancy by mutual surrender and if he doesn’t pay he would have to sue for breach of contract - he may well not have the means to do so. There may be some case law around such circumstances by now. @David122 may know as may OR. Best to persuade prospective tenant that he should sign surrender as he clearly can’t afford either the rent or to be sued by you for breach of contract.
I’ve been told govt was informed of this consequence of RRA and their view was that LLs should hand over keys and evict in due course when eg 3m rent arrears have happened. So basically (allowing for 4wk notice then application for possession then average 6m from grant of possession to eviction by bailiffs) you can assume a year of rent free living by the tenant, and you’ll never get that rent back.
I doubt many LLs would hand over keys in your circumstances, even if tenant miraculously finds the funds on Monday. I would want proof of receipt from OR or your bank before handing over keys.
@David122 advised previously you need in writing that contract cancelled rather than a deed of surrender (as tenancy hasn’t started) Tenant has yet to pay deposit or first month's rent - #14 by David122
Also advice from him that unclear whether you can withhold possession/not hand over keys with no clear legal opinion
Good luck