As Friday is missing from your list, can I respectfully suggest you visit Street Diner - the Troll is there with his burgers as are loads of other fine eating establishments.
I took your tip and visited this pop-up location with Katherine (who conveniently had no money in her purse) and went for the simple option this time, just burger bun and cheese and some sauce. Following on from our previous discussion I think simple is better with this guy as it allows the flavour of the meat to push through. If you have the caramelised onion burger you need a good half pound of burger for it to balance properly. I have tried this, but I cannot do it every time.
I love this guy, his burgers are the best in Brighton and I really hope he makes a huge success of his operation.