In reply to Offwidth:
Not all 3 Peakers are doing it as part of an organised charity gig.
Someone I know did it with her husband:
Train from Nottingham to Fort William, run up & down Ben Nevis.
Cycle from Fort William to The Lake District, run up & down Scafell Pike.
Cycle from the Lake District to Snowdonia, run up & down Snowdon.
Cycle from Snowdonia to Nottingham.
6 days door to door. Nice relaxing low impact week.