Hello Pippa - What a beautiful machine! It is a transverse shuttle from about 1900.
The name William is a brand name, probably of the retailers rather than the manufacturer. You need to see what it says on the brass badge behind the bobbin winder. I can read the German for sewing machine when I enlarge the photo, but what does it say at the bottom of the badge, and what is the picture in the middle of it?
You have missed out the tension discs when you have threaded it. Looking at the third photo, after the wire hook at the top right, go down and round the tension discs, then up to the take-up lever at the top left, then down to the last hook just above the needle. If you watch my video "How to Thread a Little Vesta" (see the sticky thread at the beginning of this section for the link) you will see what I mean. Watch until the end when I show the machine at the same angle as yours is on the photo.
As for the bobbin winder, really I would have to have the machine in front of me to show you how to thread it. I know what I would do, but explaining it is another thing.
Have you cleaned and oiled the machine yet? Is the shuttle there, and were there any feet or attachments in the side compartment? Have you got the cover? - of so, post a picture please, because that can help sometimes identifying the machine.