There are about 250 species of solitary bees in UK. They do have funny names, such as Hairy Footed Flower Bee, Wool Carder Bee, Mining Bee, Sweat Bee (!) Yellow Faced Bee, Mason Bee for example.
(I'm a member of the Norfolk Wildlife Trust and encouraging bees is one of their aims)

Apparently. 90% of our British bees are solitary.

I buy lots of packets of seeds of bee- and butterfly-loving annual flowers, and get lots of different nectar and pollen-seeking insects.

Most of our neighbours and I have little bee 'houses' of hollow sticks covered in a sloping roof, where solitary bees can overwinter in safety beside a south-facing wall.