" . . too reliant on the EU, unable due to EU regulations to look elsewhere for better trade deals." That sounds, GG13, as though you may think that we can only sell to the EU, and buy only from them. If that is your impression, no, it is not true. We sell to all the countries that the rest of the EU does, and buy from all the countries that they do, under the terms that the EU has negotiated - which are far better trade deals than we could achieve on our own.
Why should any country or trading bloc give us a better deal than they would to a vast organisation like the EU, a much bigger market for import and export than the UK? Each separate deal that we make with each of those countries or blocs will be less to our advantage than what we have in place up until 31st October.
When we leave, prices of incoming goods will rise, and the prices we get for exports will fall. That doesn't need an expert in international trade to predict, it is obvious that if there are customs duties on goods, they have to be paid.