It used to be the case that this wall needs to be half-hour fireproof
and you need building regs approval. I have no idea if this is still
the case; I would check if I were you.

I thought conservatories were a specific exemption to this. Does anyone know
for certain?

In case it makes a differerence, the floor area of proposed conservatory is
approximately 11m2. The ground floor area of house (terraced) is about 36m2,
giving approx 72m2 total area on two floors.

Christian.