Actually, you know, you just need #1 if you're hiring people who aren't in their early 20s, or something. Most "help us solve hard problems!" technology firms/startups in London simply don't pay that well, and that makes it hard to attract the older, experienced developers with families.

Hiring contractors is another way of quickly getting access to a very large pool of skilled workers, but I find that most smaller companies never bother, even though the TOC of having a contractor on board may not be all that much more than a permanent employee.

Just to add to your post, an (unfortunate) reality for many companies looking for good back-office (IT) developers is that many of the most qualified just aren't interested in the company's work or industry, which requires even more focus on #1 and #2. In my experience, many of these same companies don't understand why they can't find people, but can't fathom addressing #1 and #2.