The bad news was that the Bangkok to Chumphon tickets only go on sale 30 days before travel. Further bad news was then to be had - all 1st class tickets on the train were booked! But we could book a 2nd class ticket to Lang Suan 60 days in advance and get off a stop early at Chumphon for just a few baht more. We were charged 6185 baht for the 4 of us in 2nd class sleepers almost 2000 baht cheaper than 1st class.
I took the plunge and booked it. Should add to the experience! Looking forward to the catamaran trip out to Ko Tao and eventually relaxing on the beach. GT Adventures a company near our hotel have already offered us some resort dives for £40 each and a speedboat tour of the island for £120 for the full day.
Less than 7 weeks to go now!