I'm looking to part exchange my car but I want to take the private plate off. Do I need to receive the new V5 with the original registration number before I can P/X at the garage?
CarShop requires people who're trading in vehicles that previously had private plates on them to present the V5 when they take the vehicle in. They're prepared to make an exception though for customers who leave a £500 refundable deposit. Other dealers might offer such an option but they're not obliged to:
https://www.carshop.co.uk/latest-news/plate-retention-what-you-need-to-know/