Mining no, fishing I can guarantee yes if we can undo the common fisheries policy
Why would the fish be more expensive, particularly if we can agree a free trade agreement. The French, Spanish and Dutch see the value in fishing in our waters, so why would we not decide to. If the French do not want to buy them then fine, we will sell them elsewhere.
Why would there be a free trade agreement with the EU?
You can't have it both ways. Leaving the club and still using the club.
That also does not work with your local gym. Why should that work with the EU?
Trading will get a LOT more expensive for the British.