I asked a similar question a couple of months ago and never received a reply, so I'm trying again.
We are planning on taking the National Express coach from Heathrow to Paignton on Saturday May 7th. I was planning on purchasing the tickets at Heathrow after we arrive, but am unsure as to what is best. Do we buy tickets in advance in order to ensure we have a spot on the coach, or do we wait until the day in case our plane is late? The coach seems to depart every 2 hours, so it'll be a long wait if the first coach is full. If we purchase in advance, are we stuck (as we would be if we purchased advance train tickets) with taking the specific coach time we booked, or can we take a later coach if our plane is late?