Hard fitting the bulb before filter on the 2.2dti but not impossible, reason is both inlet and feed from filter are on top of filter body that's why the fuel runs back to the tank as soon as you open the system, like when fitting a new filter (vauxhall say you need a priming pump when doing this but they never used it on your car when I sent it for a service years back).The link as you say Mark need's correction and I would never use easy start on an engine, but have seen it used by the RAC on James's car when the wife had it

Now I have done this job a few time's on the 2.2 Dti engine and have the correct locking kit to set things up after (if you need to remove cam shaft) which I find easier than trying to get top seal in with cam shaft in place ( which I think is what the dealer did on my brothers engine). I think this is how the small nick in the seal got there.
James the fuel line has a 10mm bore so get the correct bulb as a lot state they fit the Vauxhall but have a smaller connection. There are lots on the bay for just a few £'s. I have one with a clear section in the outlet side which helps when bleeding the system I think !!!
