Tim Boler 

I only ask questions, I don’t give advice 

But you may find this recently updated UK Government guide useful:

assets.publishing.service.gov.uk/.../A guide to making your small block of flats safe from fire 2024.pdf

Splendid! Very appropriate and written in clear language. :-)

Thank you, that's a useful guide. Since the flat is a converted semi there are no other flats bordering the loft space, so there's no risk of fire spreading into another flat from the loft.

Tim Boler said:

Since the flat is a converted semi

Is there not a loft above the other half?

Yes, but there's a brick party wall that separates the two lofts and extends above the roof line to form a parapet wall with chimneys.

Tim, thank you. I know what you mean and there is no doubting that situation. Nor was I doubting you, but party walls in the loft space may not be complete.

I agree with Chris about the party wall ;) Same as inside chimney breasts, the bricklayers knew that it would never be seen so were perhaps a little slapdash, leaving out bricks, thinner joints etc. 

You might never see it in semi detached, but I've seen steels from next door's loft extension in a terrace house loft space

I agree with Chris about the party wall ;) Same as inside chimney breasts, the bricklayers knew that it would never be seen so were perhaps a little slapdash, leaving out bricks, thinner joints etc. 

You might never see it in semi detached, but I've seen steels from next door's loft extension in a terrace house loft space

OlympusMons said:

I agree with Chris about the party wall ;)

Me too, having heard a number of discussions on this topic. There are a number of issues to consider depending on age and original construction. In certain properties, roofs weren't built like they are today, so regardless of the integrity of the wall, the roof itself, or supports,  might spread a fire to next door that way

Some properties were actually built without a wall partition in the loft between neighbouring houses/shops etc, and walls were added later for security (but not necessarily fire safety).

etc. etc.