Looking for aftermarket winter wheels for my 15 XF 5.0 with staggered rims
 

I was under the assumption that the wheels were the same for the XJ and F type with the 10.5 and 9 rims. The ones I'm looking at have a 35 and 42 offset and are 10 and 8.5 inch wide but the seller said that they don't fit the XF Supercharged. Any thoughts out there on if they are right or I am right? Would going .5" smaller affect the tpms? If it helps these are the ones I am looking at. Kind of need an answer today as ebay has a 15% coupon that ends tonight. Far too hot here to pull mine and measure right now. https://www.ebay.com/itm/4-Wheels-20...ry!17601!US!-1

From memory they will fit, and the fronts will be perfectly OK, but the rears will stick out too far.
Stock XF SC and XFR rear wheels are +66 offset so changing to +42 offset will make them stick out an extra 24 mm which is pretty much right on the limit before they stick out past the wheel arches.
But the stock rear wheels are 9.5" wide so 10.5" wide wheels will stick out an extra .5" or around 13 mm, which means a total extra stick out of 37 mm which is way too much even before you put tyres on them.

How sure you sure about the 66 offset? I seem to see conflicting reports on that. I also was quite certain the stock rear rims were 10.5 as mine measure about 12 inches from outer edge to outer edge plus they came from the dealer I got them from put 295/30r20s on them which according to tirerack doesn't fit onto a 9.5 rim and they don't seem at all like they are squeezed on there. The ones I'm looking at putting on are actually 10 wide which would put them out about 31mm then compared to a 9.5 rim or 18mm compared to a 10.5 rim. The seller claims they fit a S type but has no info for an XF and none of his wheels are listed for any XFs. Other sellers list similar offsets to a 42 and a 10" rim fitting the XFR so I'm bigly confused now. :)

I agree but my problem is I already have tires (well all season Conties that were on sale and had a rebate in May as the dealer put on summers before I could convince him to go with cheaper all seasons when it was in getting its CPO cert. I don't drive it much in the summer so it will take 2 or 3 years until I can wear down these summer tires and hate the thought of swapping 'em twice a year.

I know for a fact, coz I owned one, that the stock XFR rear wheels (Nevis) are 9.5" wide and +66 offset.
I'm not entirely sure about stock XF SC rear wheels as that is an XF model that was never available in Oz, but no way on earth were the stock wheels on an XF SC any wider than on an XFR.
If your XF SC came with 10.5" wide wheels then they were not stock, and yes 295/30ZR20 tyres are stock fitment for OEM JLR 20" x 10.5" wheels, I have those exact sizes on my F-Type and they are also the stock sizes for the XFR-S.
Adding it all up I suspect your SC came with XFR-S wheels, which I believe are not +66 offset and more like +49 I think.
Best if you whipped one of them off and "read" the size, both width and offset, which will be stamped or printed on the inside either on the barrel or on one or more spokes. Then you can accurately compare with the advertised wheels and figure out if they will fit or not.
Also, I missed that the advertised wheels are 10" wide rears not 10.5", sorry about that!