Posted: 15/11/2016 at 18:24
It depends what you're after. I don't want a volcanic effect and I've been happy with the range from suppliers such as Chilterns, Plant World, Suttons and T&M but if you want more esoteric varieties and a range of heat then you need a specialist.
These people have a DEFRA certificate for quality - http://www.chileseeds.co.uk/chili-seeds.php and a wide variety of heat, size and flavour in the chili seeds offered.
If you google chili seeds+UK you'll find lots of specialist suppliers out there who rely on recommendations and repeat business for commercial success.