Installing PSoC Creator and the First Touch 003 Kit

 I resolved this issue myself.

But for the benefit of the dev team and others:

The problem wasn't that Keil C51 was not installed, as it happens it was! However the registry keys which specify the location of the install were missing. I manually added the registry keys and the prerequisites now pass and the kit installer now works.

Projects build and run successfully too.

I think the problem is that the PSoC Creator install did not create the registry keys, possibly due to this being a 64 bit install of windows 7 into a virtual machine.

 I should also say, one issue still remains - the 'Download' link given in the Kit installer to download KEIL doesn't work. I have worked around it, but others might still get caught out ;-)