the advice with these is to take out old wood and reduce new shoots by half, after flowering, but that might mean its not small enough for your garden. It does flower if allowed to get to 6 or 7 feet, I've just cut one back today, now that the flowers have finished, and it was about 7 feet high.

Try it. Mine has bushed out low down with careful pruning and it has flowers right down to just above ground level.. The tallest branches are now about 6 feet but I'll cut them back to about 5 as soon as the flowers are over if not before.. It flowers on older wood anyway so you don't lose flowers unless you cut everything back wholesale..

Its not really worth waiting for the berries as they are mingy little ones. Mine are anyway - nothing like as good as the wild ones.

Thanks everyone, at least I know I can prune it and still get flowers next year.