for bees, honeysuckle is great if you have the room, I have an old unknown variety which takes over my garden every year but I love anyway as it is always swarming with bees and smells divine, especially in early evening. It also seems to provide hibernation cover for loads of ladybirds too as mine seems to be effectively evergreen. It also has autumn berries which I suspect would attract lots of birds if there weren't 7 cats in the vicinity (only 2 mine but they all pop in). For hoverflies, potentilla (I think that's how it's spelt) seems to be a favourite from observation or was in my garden till i ill advisedly pruned it and it died