If you get a crop, why not save your own seed? That's the way to develop a strain that suits your climate not someone else's!
I know I should - but I also know what I'm like... Not terribly organised! ::)
I'm trying to improve though - and I must say I'm rather intrigued by the posts elsewhere on the forum about true potato seeds. I'd never heard about it before (but always wondered whether the fruits actually could be used - actually thinking about it I'm feeling a bit dumb, I don't suppose nature would bother about the fruits if they weren't useful for propagation!) but would be fun to give it a go.
As for the butternut - I suspect I'll have to wait and see whether a crop is forthcoming first! The closest thing I've tried so far was just bog-standard courgettes which did TERRIBLY well (only for me to realise I didn't like it as much as I had thought I did...) and aubergines which didn't crop at all.
Just a case of fingers crossed, then!