Jon - As you can see by this page, http://yourhome.honeywell.com/Consumer/Cultures/en-US/Products/Thermostats/Non-Programmable/Non-Digital/Default.htm

Thermostats are broken into two categories:

1. professional

2. do-it-yourself

I think what you are saying is that in Britain, only professionals should attempt this. In North America, they seem to think that we have enough know-how to do it ourselves, if it is low-voltage.

I don't think Honeywell would risk a law suit.

BTW - I am impressed with the wide range of products that Honeywell manufactures and no longer believe that my thermostat is cheap junk. Seems to me that they are a very reputable company.