Change of property / building works

Hi,

I recently moved into a property where the landlord, advertisements and letting agents stipulated I would have a roof terrace. When I actually moved in the "terrace" was actually a closed off section (balcony style) and the landlord informed me there was a delay on completing the work and that it'd only take a week and would being in a few weeks.

The builders have started work however they've stated that they're actually converting the whole area into another flat over 8 weeks! The council website also indicates he applied for planning permission to build another property.

What are my legal recourses / what can I do? I have no intention of paying a bloated rate (my rent rate was agreed based on me having a terrace) and I work from home so I definitely don't want major construction work going on for the next two months.

N.B. I have the original advertisement that indicates it has a roof terrace and also have correspondence with the letting agency indicating it's a roof terrace and the delay on it's completion (they are also getting me their correspondence with the landlord indicating the same)