Actually, that one will probably go in from above if you give it a little squeeze - I fitted one to my Lagonda which I put in from above, then you just need to use a tool of some sort to fish round under the dashboard and get the little peg in the chassis slot.
With the Jaguar, the problem is that it has aero screens with a diecast divider, so it can't go in from above. My steering wheel needed replacing too, so I first got rid of that by filing off the knob in the centre of the peg holding the broken piece of steering wheel in place. Once that was done, and the broken bit of wheel and its peg out of the way, I cut two long thin strips of sellotape, doubled them over so they stuck to themselves all the way along except at the end, where I attached them to each of the 2 aero screens - I hope that makes sense - essentially, it made it look like each aero-screen had a huge long antenna of tape sticking off the top.
Then I bent the 2 long bits of tape round so they were curved and fed them under the dashboard and into the 2 holes for the screens, grabbed hold of them from above the bonnet and pulled. Because the screen is made of flexi-material, it was able to bend round and be pulled into place from underneath. Then I just used some tool or other to get the peg into the chassis and carefully removed the tape. Then I fixed it a new steering wheel, and it was done. The same procedure should work for a car without the divider, but as above, I'm sure this will go in from the top.