<<PPL(H)s can cross Heathrow. However, I would advise that they know the AIP procedure inside and out. We find a great diversity of apparent ability in following the procedure, and it has been known for ATCOs to turn helicopters away if they have any doubts as to the pilot's ability to get it right. >>
Hear hear! I don't know who you are Gonzo but were you there when this one happened: PPL in a Strimmer (R22) was told "After departing xxx cross 27L, etc" and we lost sight of him.. The Lighting Op suddenly hollered "He's on 05 by the southern dual". When we told him to cross 27L he thought he had to land and air-taxi across!!!!