And the landings have to be to a full stop (FAR 61.57(b)(1)). Touch and go's don't count as they would for UK currency.
Also, you need a radio telephone operator permit (and the aircraft a radio station authorisation) issued by the Federal Communications Commission to operate the radio in an N reg aircraft outside the US.
Finally, be aware of Article 140, Air Navigation Order 2005 which prohibits the taking of photographs from or performing aerial work in a foreign registered aircraft over the UK without the permission (readily given) by the Secretary of State for Transport. This extends to paying an instructor for a BFR. Solution? Fly to Le Touquet and do it there!