Well, in a way you have - if you'd reduced the topgrowth at the top, you'd have encouraged growth from lower down, rather than pruning out the older stems at the base. Amazing you've had it ten years, these are shortlived plants in the UK, but if you don't like the way it looks, you have no choice but to reduce the topgrowth by at least a third in order to encourage growth lower down. You may need to take half off.

thank you Bamboo for your speedy reply , i will follow your advice when the plant stop flowering.doogiedog

When does it cease? I thought it went on for quite a lot of the summer, but pruning of this nature should be carried out before end of May, preferably, or you'll be getting new growth that hasn't hardened off sufficiently when winter comes.