According to Flightradar, the BA297 on 20th April was operated by G-ZBKF.

According to the Wiki in the WiFi thread, that 787-9 is one of the 4 out of 18 that does not yet have WiFi.

You can often normally see whether an aircraft has it fitted before boarding by looking out the window. If you see the WiFi dome you will know it's fitted with it