Hi seafire,
Your BA207 trip should be on the 777-300ER which will be introduced onto the BA207/206 Miami route shortly after the 12th and final example is put into service (currently forecast to arrive at Heathrow on the 12th August, followed by Miami launching with the 77W a few days after). This will have the latest seats/IFE (Thales).
Unfortunately, your 747 trip on the BA208 will have the old system and the old seats.
As for aircraft registrations, these are only decided a maximum of 3 days in advance and are liable to change. If you want to know your reg, PM me the day before.
External camera views have long been on my wish list too but BA says the extra weight and maintenance means its not worth it. Who am I to argue? Once the short haul refresh is finished, there should be an announcement about refitting the Rockwell Collins IFE aircraft with a new product. Maybe this will come with external cameras? Who knows.
Enjoy your flights and let me know if I can be of help (I can't sort upgrades though so don't ask me about that!).