Padddy - i did some investigation into cross pollinating. I get the feeling this is for the advanced class haha, maybe that's my project for next summer?
Here are my 20 semps split across three separate containers. I got home from the garden centre and realised i don't have plant labels. For now i've done a map and a key and i'll mark up when my labels arrive next week.
I got this container today especially for my semps. I've used John Innes No 1 and made sure that there is a good gravel covering above the compost to avoid residual moisture damaging leaves which happened on my first container (always learning!).
I got also got this modern looking square container. The wife advised it would look a bit baron with just semps so i added the spray painted, yes that's right spray painted Calluna.