Heated jets are easy enough to retro fit. The Barge has the potential to heat the washer bottle, which whilst not fitted, is a couple of hoses that run from the hbv to the bottle and back, so would be easy to retrofit. The jets are heated though 
Guess that Jaaag chose to save 50p by not cutting a couple of notches above the front doors for the retaining clips for the grab handles and another 50p not fitting the handles...
Does the XF have handles that might be retrofitted to the XJ?
Heating the bottle isn't going to help if the pipes and (in particular) the nozzles aren't heated. The bottle isn't subject to much windchill, which is why cars have heated nozzles. I am of course making an assumption mine hasn't got them, but the fact they froze. Its is of course possible it has them, but they are bust. If I CBA, I'll go out and look for any wiring to the wiper arms

No idea on the lack of a passenger grab handle. Rear passengers get them, just not the front. Does seem a significant oversight, even if its for technical reasons (the shape there, along with the sunroof cassette, doesn't look conducive to fitting any). No interest in retrofitting any unless it was a pure plug and play operation, mostly because its not often I'm in the passenger seat at a time when I feel I need a grab handle. And for anyone else in the passenger seat, well, they chose to get in.