Double height extension?

[Summersunny]

I posted before about selling my flat and I got such great advice that I've come back!

I've seen a shared freehold Victorian flat that is both the basement and ground floor with a huge private garden.

The flat itself is not big enough, but I would have about £100k left over to extend and the garden is nice and big so could go into it.

What are the planning permission rules on double height extensions? And if it's shared freehold, would the person who owns the 1st &2nd floor flat have to agree?

And is £100k enough for a double height extension..?!?

Are you meaning to extend a whole new basement area? I would expect that to be very expensive indeed!

What space are you needing to create ie. types of rooms?

It's a funny one as the lower ground isn't really a basement if that makes sense? It's not dug down. It's one of those Victorian houses a bit like this attached (though not this - I just grabbed the random house from google images).

Flat is the lower ground and ground. The lower ground goes directly onto the garden and I'd want to extend the kitchen out on oh and a new bedroom up on ground...

*Out on oh - I mean out onto it (the garden)

I can't see this being easy - the other freeholders will undoubtedly make life difficult, plus you might have to pay the other freeholders a substantial amount proportionate to the increase in value.

Oh crikey - I didn't know about paying the other freeholders! Is that because it'll be a big disturbance to them?

Just bumping in case anyone else has any other info...