Inherited currants - rejuvenating!

[w33blegurl]

On my allotment I have inherited a very overgrown row of currants. I know it's a mix of red white and black (random pile of labels left nearby...) but no clue which is which, other than the one at the end is a red! They are pretty spindly and have been overgrown with weeds and brambles for a couple of years. A couple had a handful of currants last summer. I'd like to try and rejuvente them and see if they can be salvaged but I'm not really sure where to start! I'm just clearing all the weeds etc from around them but what next? Should I just hack them right back and mulch and hope to get something next year from them or is there a better way? Should I be treating the different types of current differently? Any help gratefully received!!
Thanks!

[BUFFS]

if it was me I would chop back half of each plant to try to encourage some regrowth, and hopefully with the weeds gone you should get an idea what is what and be able to label each one before you chop the other halves. I would give them some BFB to give the roots something to work with, given a chance plants will thrive..

[sparrow100]

If you scratch the bark on the currants, the blackcurrant will smell blackcurranty.

For the blackcurrant I'd take out the darkest of the shoots, up to about a third of the plant and right down to ground level to encourage more shoots to form, plus any that are really low-lying as they aren't easy to pick from or crossing over. Fruit forms on last summer's growth, so the darker shoots will be the most unproductive.

Red & white currants don't smell curranty when the bark's scratched and pruning for them is the same as gooseberries. I'm very bad at this so here's the RHS advice: https://www.rhs.org.uk/advice/profile?pid=332