we're entitled to use the front entance to collect post and as a fire exit, however the landlord built a corridor from the front pub entance to the stairs leading to our flat. This was done without telling us and despite looking hideous now provides the landlord with access to the cordoned of section of the pub. Im concerned that they will be sending builders etc. into the pub. is this legal??

The owner can do anything within the law to his property. Again ''WITHIN'' the law. If you feel there is any code which may have been violated, you can nicely let him know. If corrections are not made, you can report him.

Ugly does not matter, but l am a bit unclear how this affects you except making it harder to get your mail. Making such structural changes usually requires city permission, check to see if they got it.

What you described is very hard to picture. But it does not matter. Every location is different.

l would call the local building code enforcement and get them out to see it. It could even be that the owner was required to somehow block the pub from a living area.