Posted: 07/08/2014 at 12:27
First, yes, there are single-flowered hollyhocks, but you will have the same problem with rust - if you're in an area prone to it, it's very difficult to get rid of it in hollyhocks.
One plant missing from your list is scabious - look at small garden varieties if you can't fit the taller wild plant. Bees are extremely fond of them.
Another is antirrhinums, particularly the varieties where the bee has to climb into the "trap".
As a general hint, double versions of flowers are often less attractive to bees because it's difficult to reach the heart for the insect.