Doesn’t the negotiated deal with the EU cover everything already ? Obviously the deal is in the favour of the EU and I suspect any future ones will also certainly ensure the EU don’t get the rough end of the stick
If we stay in, then the trade deals remain as they are. All of it is agreed centrally. So we can’t sort any deals whilst part of the Eu.
If we leave then we will be able to negotiate with Eu countries as well as the rest of the world and sort our own tarriffs. If we do hard brexit then I’d imagine the hardline taken by Europe as a whole won’t be mirrored on smaller individual deals as certain countries won’t be able to refuse our trade.