yes, use the bike bay in Grosvenor square if going by bike.
You can get ther at 0630 and queue up and still wont be turned away... but I'd say 7am is best...then you should be out of there before 9am. Parking charges start at 8.30am though.
Don't forget that phones, key fobs, memory sticks, headphones, or any other electronic devices of any kind are not allowed in the Embassy even if switched off.
I'll send you my number so if you run into any difficulties (even with the paperwork) just let me know.