Everything is normal UK stuff until your first contact with a "Heathrow" call sign, as it will say in the ATIS. Then they want your type and ATIS received letter and any other guff you were asked to give. Also, although regular users take it for granted, they do have an excellent understanding of your capabilities - so you are very unlikely to be asked to do anything your aircraft is not capable of. Lastly, taxiing is night is a breeze - "Follow the greens" but daytime can be a bit of a trial as some the clearances may have a fair chunk of the alphabet in them. On departure, you will also make the acquaintance of the lovely TSAT/TOBT system. If you haven't bumped into the thing before, worry not. Your dispatcher will explain all.