You can get all the way to the mast on a bike, if the barrier is closed you can still get round it. They close it to stop downhill mountain bikers driving up there. It is only a public footpath. They are also doing work on the mast, so you can't ride under it at the moment. But you can get nearly to the top on a road bike. I only went over it yesterday on my mtb so my information is up to date.