Thanks so much to everyone for the help on this - I have bookmarked all the websites.
I was browsing Helen Howes website last night, (she has a very pretty hemstitcher on there), and had a look on the off chance that she would have a suitable feed dog assembly. Well, blow me down, it seems she has!
Sent a picture, she agreed it looked the same, and while I was on asked about a replacement upper blade. She sent me a link, and I'm sure I can see a similar blade to mine there. I've told her to send both. The feed dogs are only £3, so no great loss if they are no good, but fingers crossed for the upper blade.
Sandra, I would try Helen first, she has quite a lot of feed dogs listed, and if it's an old machine like mine, you don't want to be spending a lot. She is also trying to get rid of her OL supplies.
Jessie