UK Landlord Forum / Life

A bit of background:

Been living in this property for 2 years, last week we get called by a different estate agent
than our usual one to tell us our landlord has decided to sell the flat and that viewings are going to start:

First of all our estate agents should inform us of such news not some unknown new players?
Second of all I insisted that I should ask the rest of the tenants if this was ok and that he should call me back to confirm.

He didnt and on tuesday afternoon whilst on a quick break from work I return home for lunch I
realize I am locked outside my own property as someone has decided to lock all the locks on the door: one of them we dont use

So not only did they invade our flat without authorisation they ended causing further grief to my day by delaying me by 20 minutes
to a meeting at work and I was unable to eat.

What can I do ?

Thanks