I haven't grown Streptocarpus from seed but I would say the use of an electric propagator next time would sort out your problem as you need a constant temperature to succeed. The cool night temperatures can cause the seeds to rot off. I have found that using a whole leaf method of propagation the best but, of course, you have to buy the desired plant first.

At the same time I set Lettuce, Lupin, Cabbage, Pansy, and Coleus all of which are growing nicely and have been potted on
I knew seed Streptocarpus were tricky to get started but thought it a worth while challenge. Obviously they are of a very fussy nature and need a more constant environment.
The seed is pelleted in a coloured coating of small ball-bearing size and still look OK, they just aren't moving.
I'll try to regulate the conditions and wait and see!
Thanks for your comments Jimmytheone.

Hi, Streptocarpus seed should be sown in late winter, or spring, in a propagator, at 64f, you can take leaf cutings in spring or early summer, if your plants are large enough, you could also divide them, also in spring or early summer, Derek.

Thanks to all.
My family have bought me a thermostatic controlled propagator for my 75th birthday.
Problem solved???