This information is for travelling to Yarnfield Park, which (obviously) we are not doing in 2021. However, we'll leave it here in case people are considering the 2022 MathsJam.
Manchester is geographically the closest airport. From there trains take between 90 minutes and 2 hours, depending on the exact train taken. Some require one change at Crewe, some require one change at Manchester Piccadilly, some require more changes.
Anytime tickets are about £25 (as at May 27, updated prices still to come).
The train station is well sign-posted, but you may need to exit the building to get to the "sky way" to get to the station.
For options other than Manchester Airport see Travelling by Air.
Next: Travelling by train