Your dealer should be able to advise when this is but as a guide it will be about 8 weeks before manufacture... But do ask your dealer to check as things can change!!! And it could also affect your original delivery date!!
BTW not your problem but every time you change an option before lock down your dealer has to re-load the whole order back on to Jags Vista system which is pretty time consuming, so if you get a slightly unhappy sales guy if you've changed your options a lot that's why :shock: