Trade deals with the US were always weighted to one-side. Before now, other countries could maintain a fig leaf over that fact. Any deals under Trump would need to be so egregiously favourable to the US that no world leader will be able to sell it to their populace. I don't even expect the default WTO global trade rules to stand unchallenged over the next 4 years.
The British shouldn't get their hopes up. US trade will never replace your volume of trade with the EU anyways, and your economic output is dominated by London's finance industry. The Goldman Sachs team assembled by Trump will be working to move that business to NYC and Chicago, not support London in its post-Brexit decline.
The funny thing is that Trump will likely be the only candidate for something like 50 years that didn't depend on Goldman Sachs to be elected. Reagan might not have needed them, but they've been pretty entwined ever since. I can't see anyone else winning the primary and general without their big bucks and them proving the odds by betting on them.
Democracy suffers from such vast sums of money in the electoral system.
(one Internet Point for anyone who gets the reference)