It depends a lot on the rider and how fit they are. If they are spent by the time they get to Hardknott then no amount of low gearing will get them up.
If they still have something in the tank at that stage, then a 34/50 compact and either a 27 or 28 largest sprocket at the back should be fine.
Like others have said, it depends on what is on the bike already, how easy and cheap it will be to swap. I know folk who have done it on a standard 39/52 double with an 11/25 on the back. They accepted from the start that they would have to walk bits but that was cheaper / easier than having to faff around altering their gearing.