I’m no expert but first thought it might be a bottlebrush or hebe perhaps, you do get some late flowering hebes but the the leaf and flower shape look wrong. Could be Clerodendrum bungei otherwise known as Mexican hydrangea https://www.rhs.org.uk/Plants/29541/i-Clerodendrum-bungei-i/Details It can be a bit thuggish and sucker freely which would explain its rampant habit, apparently the leaves can smell a bit pungent.

More info https://www.gardens4you.co.uk/spiraea-japonica-anthony-waterer-gb-en.html

Spirea

Never thought of spirea, somehow I always think of it as spring flowering shrub. Well spotted Carolina:-)

Thanks everyone!

Does look like spirea, but looks rather woody so a nice cutback might be good. I have a few different varieties of spirea in my garden and some are best cut right back to ground every year, while some you can just prune the heads off.