When we are talking about decats we have to be careful not to get mixed up with petrol and diesel engines -
Most diesel engines have a small, passive cat, there is no sensor, (no wires, no EML) the cat can be completely removed and the car can still easily pass the emmisions MOT test, as only particulates are measured on a diesel, diesel Ford owners have run decats for years, and passed several MOTs, no problem, recently the rules have tighened up, now there is to be a visual inspection, so it must look like there is a cat present, on many cars you cannot see if there is one or not, as there is an engine cover at the top, and an undertray on the bottom (the tester cannot remove covers) in this case as long as the (diesel) car can pass the particulates (smoke) test its ok - as carbon can build up on the surface of the cat, often a decat reduces smoke
On cars where the cat is visible it can be cut open and the innards removed - many Ford owners have done this and passed the MOT no problem (as above, it may even help reduce smoke, especially in conjunction with a solid EGR plate )
in tests, it was found the back- box was more restictive than the cat (diesel mk3 mondeo 2.0 &2.2, other turbo-diesels are similar)
On a petrol engined car its a different matter the presence of a cat may be detected by the emissions - and it may be diffucult to get the car running right and the emissions low enough to pass an MOT - in this case a high flow sports cat is probably the best way to go for a modern, petrol-engined road car
A little update. The Ford Manual that I found this part number in is definitely for the North American van and I found a European van and the connector that does the same thing is a completely different plug. So I kinda doubt that it's only available in Ford Europe. DOn't know what I'm going to do now...
It may be possible to connect the inverter directly to the battery - theoretically it only needs 2 wires + and - (i would use heavy duty cable) , it could run through the firewall (scuttle?) this has the advantage if being seperate from the vans' existing wiring - you could add a suitable inline fuse close to the battery