Thanks, Peter :o)
I've been holding off, waiting for something from Gala. I think Karl's pretty well covered it. An ideal arrangement is for a Management Company to be set up by the Freeholder(s). This isn't always done, and leads to all kinds of mess.
Also ideal, is the arrangement where the Leaseholders pay a regular service charge to the Management Company. The fund pays for regular maintenance, and ideally builds up enough to cover major works such as mentioned in the original post.
This, being the UK, is often overlooked; resulting in bad feeling, squabbling, and fees for lawyers.