i don't see why they can't continue doing it during the night-time closed period, as at present - and just manage it better as Crispy suggests - rather than cause us any extra inconvenience.
Metronet are currently asking for an extra £1-2 bn public money, due to having overspent. According to Saturday's FT, "The official deciding on emergency funding for [Metronet] is likely to award less money for work that is behind schedule". Is it cynical to suggest that perhaps they have a particular incentive to catch up with work before this decision is taken?