The OP mentioned T4S so that's normally a BA flight, IB would be T4. The exception is that the IB longhauls to LHR which may - or may not - go from T4S.

Incidentally, when I arrived into T4 on the Nostrum service referenced above, I switched on my telephone. Just before doors opened I got this supremely helpful text message and separately an email. I'm told these are coming to BA passengers at LHR too.