Allotments 4 All

Jostaberry should I prune it like a blackcurrant ?

Yes

Thanks, is it necessary to do so ?

I just prune them lighly to maintain an open shape to allow plenty of airflow to avoid fungal diseases & good light penetration so the berries ripen evenly.
Any wood over 3 years old will rarely produce anything so can be removed.

I find I have to cut out loads just to keep them anything like in shape!!
;D

Mine is quite new.  I am thinking about buying a 2nd or should I just take a cutting.

Just take a cutting they have never failed to take for me...
;D