Am I to late

Sigh purchased two private plates for mine and the mrs car my old reg was ea53vxr got the go a head to day to change my plates over, decided to look to see what a vxr plates worth closest to mine ea57 vxr £999 can I make my old plate private or do I have to take my private plate off and hope they put my old ea53 vxr plate back on and make it private then

It's around 200 to make your original reg a cherished number plate and average price for vxr one ATM is 400, but the ea57 vxr is 1000 so should be the same with ea53 vxr. Although 400 still a good price but considering I only payed 1000 for the car would be a big bonus if the plate was worth 1000,

just don't know if I am still entitled to the plate if I put my new plate on remand and get my old plate back the make it a cherished number plate, then put it up for sale then put my new plate back on. Would cost around 360 so be worth it if it was valued at 1000 but i don't know if they would reissue that plate back to my car because it is not guaranteed Also was in a hurry when wrighting this lol