[JayG]

Probably a long shot but you don't store hormone weedkillers in the greenhouse do you BB?

Another RHS link.

[Aunt Sally]

I guess I'll have to try the resistant varieties or just buy more plants and never let them near the greenhouse! It's a waste of a greenhouse though - I'll just have to turn it into a summerhouse for a couple of years 

That sounds like the best option to me. 

I would probably fumigate the greenhouse too.  The virus is carried by aphids so it would be a good idea to eradicate any that are present now as they would be infected and could carry it over to next year.

[bexybeck]

No, I don't store hormone weedkillers in the greenhouse, but you're right, it doesn't half look like hormone damage and it is localised to the greenhouse.

Looks like I'm going to have to have an all-out assault on the greenhouse and hit it with every cleaning/fumigating product I can find!

Thanks guys!
Bex

[Aunt Sally]

Good luck and do let us know if you get rid of it for next year !

[Yorkie]

You don't smoke, do you?  Tobacco can introduce viruses.