I went to several B&L chains. The first was the original in Mayfair when during a quiet weekday lunchtime I sampled the lobseter roll, chips and salad. It was definitely good although I did feel having a whole lobster to yourself would be more exciting than a roll. This was slightly put askew when I tried the whole lobster the first time and it wasn't so succulent as hoped.
After a few more I came around. In particular, I sought out the branches that had the massive sharing lobsters (Soho and Bank). 8-10 lb lobsters are an expensive delight, but chewing through the enormous claw and tails was such a happy experience. The unlimited supply of fries and salad is a bonus too.
Grab some friends, select the biggest lobster available, enjoy.
PS. I still can't figure out why you'd come here for a burger, even if it is Goodman steak...