Dealers DVLA Reg. Transfer

[mike20]

I won’t whinge on about how long it takes to transfer a cherished number, this has been covered in other posts, however this is a related issue that I’m a little concerned about.

I’m currently waiting for my transfer to go through. My dealer has my car, with my plates already on it but I can’t have it until the DVLA get their act together.

My dealer says that when they’ve received the word from the DVLA that the transfer has taken place, then I can go along and take delivery.

Fine but I’m part-exchanging my current car that has my existing plates on and obviously as soon as the DVLA change takes place, then those plates become invalid on my current car so I’ll be driving around for potentially days with the wrong plates on my existing car.
Dealer says this isn’t a problem. Not to him its not, but I’m worried that I’ll be driving illegally.
Be interesting if I am unlucky enough to get stopped and my plates don’t match the car.
Plus I wonder if it affects my insurance?

Anyone been in this position? Please put my mind at ease!