Woking (SWR) > Waterloo (walk) > Waterloo East (SE) > London Bridge (Thameslink) > St Pancras (EMT) > Nottingham should work.
It might work out less hassle - depending on timings - to change at Luton Airport Parkway rather than St Pancras?
Another variation on my suggested route - which could be cheaper with split ticketing - would be to jump ship on an XC service at Coventry and go Nuneaton (change) - Leicester (probably change again). Slightly more exotic, probably slower and definitely more faffing about though!
And a final one (for now) - you could go Kings Cross - Grantham (change) and on to Nottingham. If, by chance, you actually want to go somewhere around Netherfield, and the timings worked out so you could get a branch train that actually stopped* there, you might be on to a winner.
* There aren't many.
All in all, I'd expect Waterloo - tube - St Pancras to be the least stressful most times, with plenty of trains if things go wrong early on in the journey.