Can the tenant prohibit the landlord from accessing the property?

My tenant has served 90 days notice and expressed his intention not to renew the tenancy. I did offer a rent reduction and also monthly payments, however, he insisted that they will move out and return to their home country.

We had agreed on a time for an agent to visit and take photos to market the property, however, they are not allowing me or the agent to access the property. Further, he has not accepted any of my many calls or responded back to messages.

Where do I stand legally in terms of gaining access, especially as he has served a written notice to vacate?

My objective is to ensure that I do not have an empty villa once they leave given the tough economic times.