Independent of settings, I don't think that such programmes should be in HDR [HLG version].
There is a previous discussion here on this.
I've had the same for on-demand from Virgin from 5, Sky Max, and U&Alibi programmes, none of which broadcast in UHD / HLG, and whereas the odd Sky Max programme is in theory available in HLG, the programme watched [The Walking Dead: Dead City season 2 episode 1] isn't, and the other two definitely aren't.
I haven't got a subscription to Sky Movies on Virgin Media, but have on Sky, and their options for September 5 are:
SD
HD
UHD
UHD - HDR [HLG]
The HDR version should only be an option on the UHD version, not the HD or SD versions.
Virgin seem to be doing something strange to their on-demand programmes, whether deliberate or not, and it affects several programme providers, so isn't down to the provider. It isn't done on all programmes in the same series, e.g. it affected episodes 2 and 3 of Bookish, but not episode 1 when I watched them, but on-demand U& programmes appear completely washed out at least on some programmes if this isn't applied.
The problem in doing this to programmes is that not all TVs will treat such programmes equally, and it gives no choice to those who get a worse picture as a result.