End of tenancy notice- guaranteed rent

Letting Agents

I have a property which is let out through an estate agent through a guaranteed rent scheme. I am keen to extract myself from this agreement but the estate agent has said this is not possible until the current tenant leaves - now over 6 months after the end of the agreement I have with the estate agent. The current tenant has now said he is leaving but does not want to give a specific date as it is dependent on a house purchase and he does not know when or if completion will happen but he says he has given a month’s formal notice and asked for some flexibility. I am happy to do this, but am I within my rights to always expect a full month’s notice of a precise date of vacation? And can I, under current conditions, show prospective tenants round now?