Can anybody tell me if Liverpool to Nottingham via Nuneaton and Leicester is a valid route on a Saver please?
No, but it is a valid route Liverpool - Loughborough or East Midlands Parkway, and they are cheaper!
Instead of buying a £45.10 SVR Liverpool - Nottingham, buy a SVR Liverpool - Loughborough or East Midlands Parkway, both of which are £42.70.
Travel outward via Nuneaton and Leicester. This is valid by map combinations BP+LC, BP+LC+CH, BP+LC+ML or BP+ME.
From Leicester, choose a train to Nottingham which stops at the destination printed on your ticket. On arrival at the destination, remain on the train but change from using the outward portion of your ticket to the return portion.
Break the return leg of your journey at Nottingham. This is specifically permitted by Restriction CG which applies to your ticket. CG also states that travel is permitted by any train except those timed to depart Mondays - Fridays before 0900.
Resuming from Nottingham on any day within a month, return to Liverpool via Chinley or Uttoxeter. Return via Chinley is permitted by map combinations ML+PS or PS. Return via Uttoxeter is permitted by map combinations CH+EM, EM or EM+NC+ML.
Return via Leicester is not allowed because that would involve doubling back, that is passing through a station more than once, which is not normally allowed. You may have to double back through Beeston and Attenborough, but that is allowed because both are members of Nottingham Group for routeing purposes, and there is a special rule permitting doubling back through group stations where no station in the group is the origin or destination printed on the ticket.
EDIT tony_mac is right! A £40.60 SVR Liverpool - Leicester is even better value, can be used as I describe without the bother of checking that your train stops at Loughborough or East Midlands Parkway, and has exactly the same routeing map combinations as I describe above.