I started to make a list of non-native plants and realised very quicklu that it was easier to make one of native plants. Probably less than 5% (that sis a guess) of the things we grow are native to this country, Sadly it became an island before most European species managed to recolonise it after the last ice age.
Even the majority of our food crops are not native, wheat, barley, carrots, sprouts................all brought in.
Insects do not care from whence cometh the pollen, just as long as it is there. So double flowers are out if you want bees etc.
The most popular plant in our garden for Bees is a Lonicera alseuosmoides. Nothing much to look at or smell, but I counted over 500 bees on it one day last year.
Ceanothus by the way is native to California.