no it's not too late. according to the RHS it needs to be done in early spring so that is now.

Thanks. I had read that it needs to be done after flowering.

Sorry Canalhopper, one source said early spring, as it flowered late in the year, but on double checking it flowers mid summer and needs pruning after flowering.

It flowers on last years wood. so let it flower this year then prune after.

if you have already pruned it don't worry it will just not flower as well this year.

Thanks Seaburn. I reread the RHS page after you’d posted, and it said to prune after flowering. No, I haven’t pruned it yet!