Honestly, I found it invaluable. For the NVR and the VR you do need to be taught how to tackle these questions. I showed some of the NVR questions to my DSis, DBiL and uncle - between us we have four Oxbridge degrees (including engineering and physics) and my uncle is a retired physics professor. There were questions none of us could do, but my DCs could having been taught how to do them! They’re like cryptic crosswords - you need to understand the rules of how to tackle them.
An experienced tutor can also teach wider exam technique which is invaluable. Eg for adaptive online tests it’s really important to spend time getting the first 10 questions right as this affects the adaptive algorithm which then determines the highest score you can achieve. This is more important than trying to complete the test.
Whereas for an old school paper test it’s important to try to complete the test, and you can skip harder questions and go back to those at the end.
Also, my son was awarded an academic scholarship and while he’s bright and capable I doubt that would have been the case without our tutor.
There will always be people who say “well if you need to tutor lots then it’s not the right school for your child” but that’s just not true for many. Frustratingly most kids are tutored which must drive the overall standard up. So it’s a gamble for your child to be one of the few who isn’t.
And the schools you are targeting are amongst the most competitive/hardest to get in (sorry!).
However, there are families who get offers from good schools without formal tutoring so I’m not saying it’s an absolute necessity, just that I do think it’s a good idea. If you’re not using a tutor then as a parent you’re going to have to do a certain amount of tutoring yourself so you’ll need to understand how to tackle the tricky questions and exam technique for the different tests.
I don’t think you’ve left it too late at all. The Atom platform offers tutoring so that would be one option or there are crammers that run during the summer holidays and probably May half term.
If you pm me I can send details of our tutor if you don’t mind remote tutoring. I don’t know if she has any availability though.
Good luck!