My DD is somewhat randomly variable and has scored from 75%-95% in NVR papers, 78-96% in VR papers, even Walsh, although she struggles to finish them in time. She's been practising Latymer past maths papers and has been getting 36-46 out of 50, she seems to find some of the papers easier than others, but I can't figure out why as they are all pitched at the same level as far as I can tell. Her English is good so she's just practising comprehensions and timed extended writing, but I'm not doing papers as such with her. I think it's down to how much sleep she's had (she's a chronic insomniac - always has been, this is not to do with the exams looming) the weather and time of the day. I couldn't hedge her chances of getting through to round 2: whilst she's perfectly capable, on a good day she'll sail through, on a bad one she'll miss by a mark or two.
She's away all week this week with school at a PGL activity centre, she sits for Latymer on Monday 24th. I'm just going to get her to rest as much as possible at the weekend, and maybe do one paper each day to remind her what she has to do, but will try to keep it unpressured as much as I can.
good luck to your DD