I had the same problem with mine. Whenever it failed to start in P, the selector position would not be displayed on the dashboard. If it did start though, it would likely go into failsafe mode. I had to start the car in N most of the time. A battery change solved it although I already had the xyz switch ordered.
Glad it all worked out for you and you weren't ripped off on top of having your gearbox unnecessarily opened up. It's really outrageous how some garages or even the dealership will try to take advantage of people if they're given the chance.

PS : Is that a hunting excursion photo?

So, soon after I had it working the dreaded failsafe came back.... I assumed it was because we opened the switch and potentially water had got in. A few months on the drive I managed to get the switch off and sent to landyman for a refurb for £50. Switch is now being put back on as we speak so will keep you posted.... otherwise it will be birch and a new gearbox or up for sale..... 🤞🏻

ouch, lets hope the refurb does the trick

it depends on how much you love the car!!
my old TD6 GB failed my own fault should have serviced it but i did not and it let go a week before i was due to go on holiday towing my caravan.
we loved the car so much it seemed worth the 2.5k to get it done after i got it back it was faultless we did another 40k in it before letting it go to get a newer car.
you can drive a brand new RR or other car off the forecourt and lose more money
the upshot is i had another year and a bit of trouble free motoring  2012 Vogue 4.4 TDV8 - Current
2014 Navara V6 - Gone
2004 Vogue TD6 - Gone
Grand Cherokee - Gone
Discovery V8 (LPG) - Gone
Discovery TD5 - Gone

So did the refurb fix the problem ?