[pjc50]

Yes, it's a disaster area. I'll just plug a small web app written by a friend of mine that addresses this problem: http://sizes.darkgreener.com/

It uses least squares regression to work out, given your actual measurements, what "size" label from which shops is likely to fit.

[tomeglenn]

This is great. Would your friend be interested in discussing a collaboration? I'm looking to build similar functionality into HipStat.