Offset quoted for a 406 is 13-23. The steels I have are 18. There is very little clearance on the inside of the rear wheels, hence my advice to check the offset. As an example, the alloys that were a perfect fit on my Xantia would not go on the Berlingo - even though the offset quoted on certain websites for the two vehicles varies only by 3mm.
The part number for the mk2 Berlingo 15" steel wheels is 5401H7 which also shows up as a Peugeot 306 part, as well as Citroen C5 (and probably others as well). The Berlingo offset, as Coco says might cause issues. I have looked for a definitive list of wheels/tyres/offset sizes, but have seen conflicting numbers quoted which doesn't help.
2005 Berlingo Multispace 1.6i Desire (Iron Grey)
If everything seems to be going well, you have obviously overlooked something.