Need some advice on what bushes to buy

Farmyard Nurseries have a good selection of Buddleja davidii varieties see Search For: buddleia | Farmyard Nurseries they are in Carmethenshire. I haven't used them myself yet.
Champion Plants in Somerset Products
If you want something more unusual try Pan Global Plants Plants for sale name search | Pan Global Plants in Gloucestershire good quality plants I've both visited and used mail order this year.
With all three of these you'll probably have to wait until spring for them to have stock of most listings.

 

Excellent, thank you!

 

I recommend Farmyard plants @TheMadHedger - they grow a massive range of interesting plants.