Anyone driving up on the day make sure you give extra time on the M1. There is a new junction being constructed and last Saturday it took me over 3 hours to drive from Kidbrooke to Northampton. Normally I can do it in under 2 hours. I have checked the RAC journey planner and from my place they say it is around 2 hours 36 minutes to Barwell. I would add an extra hour and a half to this at least.
or alternatively take M40 to Junction 15, and head towards Coventry on A46. This becomes the Coventry Ring Road then turns into the M69. The main delays will be on the M25 between the M4 and M40, and when the A46 becomes the Coventry Ring Road.
This was the way I used to go to Hinckley, which is not far away.