Purple Toadflax (Linaria purpurea). It flowers profusely with "simple" flowers. These wild things are perfect for bees because plants and bees evolved together, depending on each other for their existence. It is a sad fact that many cultivated varieties of garden plants are so overbred that they have ceased to have any value as food sources for pollinators.
 As I walk around London I see a lot of untidy gardens and derelict areas that have been colonised by invasive plants like Toadflax, Green Alkanet, brambles, Buddleia and so forth. Thank God for that- they are absolutely crucial in sustaining our pollinators.