For next autumn I'd suggest planting some snowdrops between your hosta. They like the same conditions and share the same space very well. When the snowdrops foliage starts to yellow the hosta foliage develops to hide them.
The snowdrops in the picture have been planted with hosta for many years, so I know this combo is good. In mild winters snowdrops can be in bud very early and look good for a very long time. 'S. Arnott' is a cultivar that is supposed to be fragrant, but the common snowdrop is much less costly. Needs early planting as the bulbs are susceptible to drying out. Dried bulbs = very disappointing results.
Corydalis solida 'George P. Baker' is not the longest blooming spring bulb, but it has a very eye catching color in the spring garden. I don't know if you have bumble bees where you are, but if you look at the picture above you can see the puncture marks where the large bumble bees have pierced the flowers from the outside to get to the nectar as the flower is to small for them to fit in. This tells a good story about how much they liked this early food source. The advantage with Corydalis solida is that the foliage dies back very quickly and that it prefers a shadier spot and the tuber tolerates summer moisture. So it will mix well with other shade plants. That said Corydalis solida 'George P. Baker' may not be as vigorous as some other Corydalis, so it could be worth trying a few to see what grows best for you.
Allium 'Globe Master' is sterile so blooms a lot longer than many other large flowered Alliums. Extremely showy. Being sterile doesn't stop it from being a good nectar source and it attracts a nice variety of insects. Does need a sunny spot in well drained soil. Seed heads look good for a while too. Probably best with annual lifting and dividing as the large bulbs tend to dwindle in size if not given adequate space and fertilizer. Being dry in summer promotes healthy bulbs.
I planted Allium 'Summer Beauty' this autumn, so don't know at all how it will perform, but it supposed to be long blooming and very attractive to butterflies. This one is also sterile and in contrast to most other Allium the foliage remains throughout the season and well into winter, or so I read. Anyway mine are still green.
Cyclamen hederifolium seems to be happiest under deciduous trees and tolerates root competition well. Doesn't like summer moisture, but wants sun in the winter. It is a lovely autumn blooming tuber, some selections are scented and it can remain in bloom for a long time if weather is coolish. I feel some scent from some of my common ones as well, but I needed to stick my nose in it! While it can take very cold temperatures, its long term performance is questionable in cold winter climates as it has foliage through the winter, so maybe not the right choice for you. Still I feel it needs mentioning as it is a true favorite. I've mostly seen hover flies on it.
Finally a scented tulip. 'Brown Sugar' fills the air with a nice sweet scent on warm days. I dig mine annually for summer storage, so don't know how it does if left in the ground. However every bulb planted produced one very large bulb and a few smaller ones. This is almost ideal tulip behavior in my book. You will have bloom in subsequent years and still increase your stocks
