where can I find details of countries where plants are grown commercially

Try the search engines on the internet? Such as www.flowers.org.uk/.../mai_where_our_flowers_come_from.php - and you could try open directory for reginal europe.

I would think that you have to be a little more selective with your question, Pat. I could purchase commercialy grown plants from just about any country on the planet, finance and import regulations permitting.