Wasabi? It's a member of the Cabbage family indeed related to our Horseradish but no idea where you would get one or even seed.

Poyntzfield Herb Nursery mentions it in their catalogue. They are based in the Black Isle in Scotland but do mail order, although the mail order may not be all year round.

You can phone them on : 01381 610352 or find more info on their website :

http://www.poyntzfieldherbs.co.uk/