Repossession , moving in for covid quari

Possession - Section 8 and Section 21

So sorry this is a complex one! Bear with me please.
In my house I had to tenants living. They were a couple but have split up and not very amicably! The tendency came to an end in 14th of May. I I did not renew their tenancy but send them section 21 possession notice. I also gave them 3 months notice which ends on the 15th of July to which they agree to move out by . She has already left and is a pleasant person she has paid her rent giving back the keys and everything is satisfactory with her. He is a different story firstly it is very difficult to believe anything he says as has shown to be the case over the last 2 years that they have been in the property. He also owes 3 months rent areas I have however offered to waiver the rent areas and return his full deposit if you agrees to move out by the 15th of July which he has agreed to in writing in email. He has said he will not hand over the keys until the deposit ( held in dps) is in his bank which I have agreed to so that it returns to his bank on the or just before 15th July .
I need to return to the UK and quarantine for the statutory 10 days. I have asked to do this in my house from the 15th stating to my tenant that I intend to do so there.
My concern is that he may not move out or hand over the keys. then I will have nowhere to quarantine. Would I be able to move into my own house even if he hasn't left by then?
My other ex tenant who moved out said that he said he was going to change the locks when she gave the keys back. Obviously I want him out and to get my house back
Any suggestions and advice please to help resolve this difficult situation.