thanks for the replies!
I did a complete overhaul on it today - set the timing of needle and hook, feed dog and eccentric. It's running a lot better now but still likes to look awful underneath the workpiece at the start of a run. Once going, it's sewing pretty well although the tension isn't as consistent as it needs to be. I think i'll put a new bobbin case in and maybe replace the upper tension discs in case that makes any difference.
The one thing I did notice was that I think I'm missing a threading component although I've seen pictures and videos without it,,. Before passing through the eye from left to right, I think the thread is meant to pass through something at the top of the needle. I ordered the part but it doesn't seem to fit with the way I have my needlebar configured (the way I bought it) Could someone please post a close up picture of this piece if you have one please and if anyone could cast an opinion as to whether that could be causing the problems above - that would be awesome.
Appreciate all the help!
T