I guess the likely alternative would be one of the G-GATx aircraft, or any of the LHR aircraft that may be shipped over to LGW. But that's "how long is a piece of string" - you would only know for sure when you boarded, with a heavy chance of a change coming through at T-72 hours. You could swap to LCY or LHR I guess if your ticket was bought in the last 24 hours.