jdd:

In the UK RVs use both propane and butane.  They use
"Calor gas cylinders" which are stored inside the
vehicle.  See:
http://www.caravanning-online.co.uk/caravan-gas.htm#howtoorder
One uses a different regulator (different pressure) and not
different orifices.  As this site states "butane for the spring
and summer months...and propane for the winter months...."

This does not answer your question about filling a US or
Canada spec propane tank, or what they use on the continent,
but this RV servicing company:
http://www.northcoastcaravans.co.uk/calor_gas.htm
could probably answer your questions.

Richard
Boulder