If my car has the new style number plate i.e. KV04 WHS can i purchase a private plate with a prefix i.e. T10 DJB and display it legally? Thank you in advance.
Yes, you can. That's perfectly fine.
You will need to pay DVLA fees & fill in a form (depending on whether T10 DJB is on another car or retention certificate).
If you want someone to do it all for you, www.theplatemarket.com do a transfer service. You don't have to buy a registration number through them.