I had similar issue on my 2017 F-Pace last week, dealer got me 80% from JLR. I called them and argued then demanded to speak to a manager and he came back and said they will pay 100%, the diagnostic was also covered in this.
I quoted consumer rights act of 2015, sold faulty goods and told them they have 1 opportunity to repair or replace and must do so without cost to me, in a reasonable time-frame and with out causing un-necessary inconvenience. They offered a hire car if the dealer did not have a loan car. I should get my car back next tues with brand new turbo, engine and DPF fitted.