There will be delays. It's factored into the plans of anyone involved in importing and exporting.
It'll cost a lot more than £200 million in trade as that £200 million is just the price increase in fruit and vegetables that is currently traded. A lot of people will just leave the market or restrict their participation. If delays are encountered not at the ports, then everything coming in or going out will be caught up in the chaos, whether it falls within the new rules or not.
Once the veterinary inspections for meat products come into place there will be additional delays and costs that impact the supply chains further. I've just left the Dutch company I was working for as they've decided to stop targeting the UK. They're not particularly going to be caught up specifically, but all the logistics agents they use are advising them to stay clear of the UK and charging them additionally for UK deliveries and not guaranteeing any transit times.