Here's the menu, full English breakfast and California toast in the Concorde Breakfast Room in the LHR T5 Arrivals lounge from July.
A perfectly adequate selection, let down by low quality ingredients and the usual indifferent and unpolished service. I had to prompt the lounge receptionist for a voucher to use the CBR - I do wonder how many infrequent First guests don't know of the CBR's existence when using the Arrivals lounge because of this.