Landlord wishes to increase rent & deposit for problem tenants currently granted periodic tenancy

Other

I have problem tenants who have been previously granted a periodic tenancy at the expiry of their original AST.

The tenants have previously fallen heavily into arrears which are currently being cleared via a top-up amount to their weekly rent. This arrangement was instigated as a result of a S8 hearing some time ago. The balance of the arrears should be cleared by end of September, some twenty months since their initial move in.

Discipline has therefore been restored and they have proved reasonable tenants overall whom I would be inclined to keep.

However I now wish to increase the property rent and - mindful of their early behaviour - increase the deposit too.

Could you advise me the best way in which these increases could be achieved? Eg Would it be better to increase their rent & deposit under the terms of their current periodic tenancy or insist upon a new AST altogether, upon pain of an eventual S21 eviction?

A subsidiary point: If the tenants belatedly sought regulation of their rent either before or after they have cleared their current arrears, and the regulated rent proved to be lower than that upon which their arrears were calculated, could the tenants then apply to overturn the Court judgement?

Many thanks.

TomD