Aaaargh! Hope you're leg's much better now. What a horrid thing to happen, especially in the spring!!!
Hmmm, sounds as if your blackcurrant has taken a year off - it may have been frost damage - I guess the allotment is more exposed than your garden? Do you know the variety? The ones with the prefix 'Ben' are more frost resistant than some others.
I think I'd give it some Fish Blood & Bone now (according to pack) water and a mulch of manure, and repeat in the autumn.
Next spring keep an eye on the weather forecast and if there's a frost forecast at flowering time I'd drape the bushes with some fleece - that's what I did with my gooseberries this year and it worked.