Thanks the write up on your experience of fitting 20mm Ford wheel spacers to your Sportbrake. I am interested in adding some additional track width to my Sportbrake. My experience with previous cars (Mercs) has proven that the spacers add handling improvements as well as having (in my opinion) a positive impact on the visual appearance by providing a more aggressive stance.
Having read this, I have just placed an order for a pair of Ford specific 5x108 63.4mm hubcentric spacers from ebay. Assuming that these fit, I will order another pair, however, until I found your summary I have been unable to clarify whether it was worth taking the risk of ordering these. As you correctly mention, The Ford specific parts are around half the price of any similar specific Jaguar spacers that I have been able to find.
I hope to report back with positive news in the next few days....