Well, it's taken me a while, but with MisterVimes' assistance I have finally been able to post the speed calculator I spoke of. I have even added the KPH conversion to it. The Excel file can be found here. Thanks, again, MisterV.
P.S. A big D'OH for me. This file is already available in the Free Stuff, but this version has the KPH converter already on it.
:o