Obviously with the turbo, inlet mani and Intercooler in the way it's not possible to get it to fit in the OEM position. I was thinking of moving it to the right hand D-pillar, by cutting the bottom out of the flat plate that's there currently and mounting the filter canister through the hole, so that the pipework is effectively in the engine bay and the filter is accessible under the van. I've looked around the engine bay and there are no alternative positions where it could be mounted, other than right between the timing belt cover and the rear of the van but getting it in and out would actually require removing the engine!
This is a basic mock-up of what I'm considering;

Image that set up pushed through this plate, and the pipes appearing behind the battery, then running along behind the flip down oil/coolant access panel;

Yes, that hole needs addressing too, as well as the rampant seam rash in this area.
Any better suggestions for this setup?