I wouldn't want to pay OE prices either !! Why not just do a search on eBay for the wheels you've got now ? So many people seem to swap wheels even on quite new cars you may find a set for a reasonable price. I'm not sure the previous XF model wheels fit as the suspension of the current aluminium car is totally different. XE wheels might fit of course, again, search on eBay. If the wheels of the previous XF do, indeed fit, there will likely be loads around. Those needing refurb are cheap, of course, but you don't want any buckles or cracks, so be diligent and make sure you get the vendor to confirm this.
Even S-Type wheels might fit but this would need checking out.
I haven't got the car yet so I'm not sure what the spec is. I think what I'll need are 18" x 8", 5x108, ET45 but I can't find out for sure that that's the right spec. The car's coming with 19" but I prefer a smaller winter option and higher profile tyre.
If if it is, I can get a set of new rims for £400 or so, which is roughly what Jaguar charge for 1! So I should be able to get a full set of wheels, tyres and valves for under £1k. I'm OK with that if I can just confirm the details.
Interestingly, as you suggested, the XE rims may be the same, I just can't confirm that. Anyone know if jaguar list the specs anywhere?