In reply to mcdougal:
> I've managed to destroy my front brake caliper and have no experience in replacing bike parts and, although it looks quite straightforward, I have a few questions:
How did it break? Are you certain it's actually broken, and not just in need of adjustment? They're usually quite reliable components.
> The old unit was a Promax 330r, does anyone know if it will be easy to replace?
Yes, quite straightforward. There are some good YouTube vids if you get stuck, but you probably won't need them.
> If I can't find another Promax, are other units a standard size?
The unit itself is a copy of the SRAM Avid BB5; the spares for this would be a like-for-like replacement, and are widely available.
> Are the bike part online shops still open?
Most are. I've had three deliveries from Chain Reaction this week.