@David1542 Hosting for a specific event in your area can be tricky. I also have guest booking up to a year in advance for popular music festivals in my area. Do you know how far in advance people will book? Also, do you know if the search engines will pick up on the information in the parathesis? If not, you could change the name to "Cheltenham 2018 Festival Ready".
You will want to time your listing going live to coinside with the usual booking time for the festival. New listings get a temporary search boost so you would want to take advantage of that.
Good luck!!