UK Landlord Forum / Life

I am actually a tenant but have a question about a property that i feel would better be answered on this section so i apologise if this needs moving.

I am in a property which has two sections each with their own front door and no access from one to the other. One section of the property is a HMO and the other is a self contained flat/ studio. The flat is 107A and the  HMO just 107. The issue is the 107A address does not exist on Royal Mail's Postal Address File (PAF). I need to change my bank details, apply for a credit card, update my address for the electoral register etc. And none of this is possible as they all say my address doesn't exist.

I assume i would need to speak to the council or get my landlord to speak to the council but i am concerned about the consequences of this. I assume, and please tell me if i am wrong, that this means planning permission is unlikely to have been obtained for this? I am worried if the council don't give retrospective permission or my landlord does not take kindly to me doing this that i could end up being forced out. (Would planning permission be required if already declared as a HMO? how would i know if it has been declared as a HMO?)

If anyone can give me some advice on dividing properties in this way, who would need to be notified and what changes would occur (e.g. To the PAF) i would be grateful as i am not sure what to do.

Thanks in advance.

Stuart