If its a charcoal BBQ I'd actually keep it ridiculously simple. Beef, salt & pepper. Let the BBQ do the work. Experiment with the cut of beef used, I really like using topside or braising steak & mincing it.
The HFW burger you mentioned is indeed immense, one of my faves when I cook on the griddle.
just done a google search for "hugh fearnley-whittingstall bloody mary burger"
and this thread is second in the results
subscribed, lots of nice recipes here for the future