Why can't small firms adjacent to the Silicon Roundabout get BT Infinity?

I has just approved a comment to my “How Rural is Smithfield?” blog entry from a small firm in Shoreditch pointing about that they cannot get the BT Infinity, Fibre to the Cabinet, service  from their fibre enabled exchange:

“Ah, totally agree. Let’s also discuss a fund for those small/home-based businesses stuck on Exchange-Only lines shall we? FTTC is unavailable to us, despite being wired into a fibre enabled exchange (Shoreditch) and not one authority, provider, regulator, or council seems to give a hoot. As a small business providing consulting services remotely a 6mg down contended ads line is insufficient. leased lines, Ethernet, bonded ads, wireless are all prohibitively expensive (£300-500/month).Silicon Roundabout? Where?”

I would welcome comments.