Matthew – if you let comfrey flower before cutting it back for mulch/compost, bees love it. My compromise is keeping my prime ten comfrey plants for mulch and compost whilst letting one other flower for longer.
Tomatoes tend to attract bees. I grow mine in pots so they can be protected when the rain comes, but there are always bees around them in June and July.
I started putting in some perennials last summer like Wallflower, Lavender and Lovage which have established and should hopefully flower this year. I sowed them in spring, planted out midsummer and they have survived winter well. I also grew some borage which I have left to self seed – plenty of flowers attracting insects last year.
A good place to search is the Agroforestry Research Trust website shop – they have a lot of interesting plants, perennials, shade loving/tolerant, insect attractors. They also indicate mature height, which means you can plan for everything to see sun to the degree you desire.