Thanks guys.
Good shout on the new hook. Cheapest i've seen so far.
I do have the needle plate and the two side plates. The hook does seem to be hitting the needle scarf at the right time but I'm convinced this is not the right bobbin carrier. Here's a (slightly) better pic. I can't see for the life of me how you would get a thread under that spring tensioner. I did get a thread under it by taking the carrier out and it did sew after a fashion for about an inch and a half but it was all bunched up underneath. I know you have to balance out the two tensions but I need to make sure the bobbin carrier etc are good before delving into the finer points.