ill try all the things suggested when i can quite busy in the garage tomorrow i think, pretty sure we got the back little arrow timing marks on the cams though as we used Autodata to confirm the timing first. I'll ask the boss though as it was him who done it first time round.

Quite worried about that video though, sounds the same, but there is a slight popping noise as if its firing, but its not a big enough bang to kick it into life, which is what low compression would explain. Really hope the valves haven't had a fight with the pistons though, its a 20 valver

Edit to add;
To do a leak down test i remove the belt and cams, what about spark plugs, what shall i replace them with?