Do I need Retrospective planning and Building Regs

[northyshoes]

Hi,

I am currently in the process of buying a semi-detached house with a timber annexe in the garden.
The timber annexe is literally a 1 bedroom flat with all plumbing, electrics etc but with no planning or building regs.
The vendor described this through the estate agent as a "temporary" building so therfore not requiring PP or BR.

Also, it stated that the council had agreed to the annexe and can accommodate family members as long as council tax was being paid, which I phoned the local council and they seem to be aware of it and even told me the council tax band that it was in and the vendors last exemption expiry date on the annexe.

The vendor has built the annexe on viewing to a high standard of workmanship and has butted it up against a garage that had planning approval. Also planning permission was given for an extension some years ago but was never undertaken and is now expired.

The annexe I have been told has been up for 2 years and has been assembled to all the dimensional criteria.

Please can someone let me know if this sounds legitimate, whether I need to get retrospective planning when we buy it, something else or not touch it with a bargepole!

Many thanks

Ralph