Have a look at first class too - I did the same journey recently and it was only about 10% more but I got dinner + wine on the way up and a bacon sandwich on the way back.
You don't get food on first class at weekends though.
Slightly missing the days when I'd do London-Edinburgh 1st class during the week, paid for by employer, get delayed then (entirely within policy) claim back to my personal account. Made £300 one quarter.
Even looking a few weeks ahead it's not much cheaper though. Bastards.