Does anyone here use a motorbike (or even better, a scooter) to travel to Heathrow T5 (to take a flight, rather than working there)?

There is some information on BAA's website about there being a parking space for motorbikes, but I wonder if anybody has any experience of it (does it tend to be full, hard to find a space, etc?)

Also, as I can't use the motorway on my little scooter, I wonder if anybody had a route from central London which avoids the M4.

And finally, although I'll probably leave my helmet with the bike, can one take a helmet through security as hand baggage? A search on FT brings up a number of different experiences, depending on airline/airport around the world.