Oh dear - for some bizarre reason the UK keyboard is not working now. Tried downloading iso afresh and just using that rather than customising it and now it will not work - I cannot see any possible reason why. Ah well.
Kyhi, BTW - tried to update Macrium by running Reflect from iso from mounted image but did it from pre-windows environment and in that case, you do not get update option.
Edit: I see now you said mount boot.wim from Host. Missed that first time.