Mon 3rd March: YES I do still have some! You've been lovely about taking them away so far but I've still got somewhere over half a dozen single canes, and 3-4 larger branches :)
Jostaberries are a cross between a blackcurrant and two kinds of gooseberry, to produce a thornless bush with fruit that even blackcurrant-haters are usually happy to eat straight from the bush! More info about them: https://en.wikipedia.org/wiki/Jostaberry
They grow extremely vigorously and I've just got to pruning mine. Past experience tells me that if you stick the cuttings in the ground, they will happily grow themselves a new root system. Lots available, from 2' straight single canes to significantly larger already-branched mature wood that might even fruit this year (with a bit of luck).
Smaller cuttings can be collected from the Windmill Hill end of The Ridgeway. Larger ones (being harder to transport) are currently at my allotment behind Chase Farm Hospital. If you're feeling really enthusiastic and potentially willing to help dig, there are also two well-established self-layered bushes I'd be delighted to send off to new homes...
Please suggest a time you'd like to collect -- I can be flexible between 8 a.m. and 8 p.m. at home (every day this week except Thursday), or 9 a.m. and dusk up behind Chase Farm. :) By default I'll send you away with 2-3 canes just in case one of them doesn't make it!