Posted: 28/06/2014 at 08:32
Yes, leave them to grow into nice bushy plants - they'll die down over the winter and reappear in the spring - usually flowering May and early June.
They'll self-seed around lots as well, cross-pollinating with each other and producing variations on a theme.
Some of us find them addictive!
And there's absolutely no problem with buying plants from Lidl, Aldi or where ever - if there's a bargain to be had grabbit!