First things first, sorry for the uninspiring title. Please edit it if you have a better one for the question!
Suppose I have a barn which needs refurbishing for the big Stack Exchange Gala[*] I'm holding at the end of the year. I contract a builder to do the repair work; we agree £10k for the work, to be paid on completion. There is a clause in the contract which states something along the lines of, "the builder cannot be held liable if the work cannot be done due to sickness or circumstances outside of her control". (An example of this might be some type of force majeure clause.)
Pandemic hits. She can't do the work. Pandemic clears in time for party (wishful thinking) but I can't host because she didn't do the work. I lose out on earnings I would have got from hosting.
I can't sue her for those lost earnings due to the lack of liability clause. (I'm pretty sure this is the case.) However, does the liability clause mean that can she still charge me £10k for the building work which wasn't done?
[*] Not a real gala, but if it ever happens you heard it here first!