My house has been invaded with these harlequin ladybirds, literally about 1,000 I reckon. I contacted the local wildlife organisation who informed me that they are not welcome and to exterminate them asap. They informed me that native, British ladybirds hibernate outdoors but these are not welcome. However, trying to kill them has proved interesting and involved a manual process of popping them one-by-one! Even then, some have survived and tried to crawl out of the bag. Not a nice job, but then again it was not nice having them stain the curtains and one even deposited its "venom" on my wedding dress, causing chaos, and making me 25 minutes late for church whilst we attempted to cover over the resulting blood-like stain!!
I donot like to kill animals etc, but these are not really very pleasant.