To ask tutors about this?

[FastaPastaForMoiii]

DC preparing for 11+ which is on a Saturday this year. Tutor has advised that we don't have a lesson in the couple of days leading up to it - have said they will be available by phone/email for moral support and nerve calming but no need for formal tuition. DC have talked about having a lesson the day before though (which will be after a day at school)...

Calming last lesson or wind down? I don't know.

Being a tutor I agree with your child's tutor to some extend.

If the tutor and your DC have some their respective jobs a last minute tutoring session is a waste of money and may even be counter productive.
The day before the exam should ideally not be spent studying all. Do something fun and calming and give your DC the chance to process what he has learned.

The only reason to book a lesson for the day before the exam was if your child was still distressed about not having a lesson the day before after you explained to her that it would likely make very little difference. In which case i'd suggest a q&a style session. Where your dc thinks about any questions she might have in advance of the lesson.