I'm guessing you've only recently moved in?
Ideally you need to create deeper borders; 40cm is very narrow. All but the smallest plants have a wider spread than 40cm. Though of course things can and will overhang the border edge, you won't be able to introduce much in the way of a pleasing mix of heights.
The salvia caradonna (great for bees) which you've planted already will get very big this year. It's also a plant that is 'over' by mid-July, and then has to be cut back and you're left with an unattractive stump, which can't be hidden with other plants in a border this narrow.
If, for whatever reason, you can't deepen the borders, then I'd plant it with lavenders (Munstead), plus verbena bonariensis (loved by bees/butterflies). I'd also look at geranium Rozanne, another magnet for bees.
Both the verbena and geranium are long flowering through the summer, and don't get 'ugly' midsummer like the salvia caradonna. The lavender won't flower for long, but the foliage still looks good after flowering.
As for climbers, I've found that one of the best easy, super-pollinator-friendly, ones is passiflora. There's also a more white flowered variety, Constance Elliot, which would provide a bit of contrast with the other blue flowers. You'd need to put in some wires on the fence for it to grow along.
Edited to add: all the above are easy maintenance in terms of not being susceptible to pests or disease, and all loved by bees. A bit of pruning is all, and obviously no use of pesticides or weed killers.