I'd been looking forward to the train journey from Ella to Kandy, I'd once read that it was the most scenic train journey in the world and it's almost a tourist attraction in itself.
I bought tickets at Ella station 3 days in advance and 1st class seats had already sold out, I ended up buying second class tickets for the 06:40 train to Kandy. There are 3 trains per day, our 2nd class ticket cost Rs600/pp. you can just show up on the day and buy tickets for the United-reserved section of the train, there were plenty of seats empty but we did visit during low season.
Second class was perfectly fine, the seats were comfortable with plenty of leg room and even though there was no A/C, the Windows all opened which was enough, the higher into hill country you get the cooler it gets.
You will need to bring plenty of water with you, the journey is about 7 hours. As for food,there are plenty of vendors who jump on the train at each station selling all sorts of snacks and treats, some don't even get onboard but will pass goods through the open windows. (Windows don't open in 1st class because they have A/C.)
Toilets onboard were OK, and not quite as traumatic as I read in one blog post.