Hi Sean....welcome to the Forum
It sounds like they didn't recheck the level and top it up after changing the filter, when the level will drop by the quantity consumed by the new filter when the engine is run once refilled with fresh oil.
Changing the engine oil in the interim is a great way to prolong the life of the engine. As you say, you can always take it back for the services and the oil filter change 🙂
I would however always use a quality engine oil with the correct ACEA specification which will more than likely be the same as the Jaguar supplied oil .
Quality brands are Castrol, Mobil, Petronas and some others. Try this company for accurate specification engine oils and keen prices (discount through the club as a Premium Member) https://www.opieoils.co.uk/
Cheers, Trevor