I will be flying into Gatwick from Barbados in First, then going over to Heathrow for my flight up to Manchester. The 2 flights are on separate bookings, so will I be able to use the First facilities at Heathrow whilst waiting for my Manchester flight, ie the Arrivals pre check in for a shower and the lounge post check in?
What ticketing class is your LHR - MAN booked in?
Also, if you are on BA, try here!
http://baflyer.com/forum/