The cheapest ticket is the direct train to Waterloo via Ascot, which stops at many stations en route.
There's a middle ticketing option where you could travel via Ascot or Guildford (some of the via Guildford timings are as good as taking direct trains, but you'd struggle to get a seat from Guildford to Waterloo in the morning peak).
Missed this yesterday...
Is this a different ticket option?
I commute from a station between Wokingham - Reading to a London suburban destination which is on the SW main line side. My season ticket for this costs the same as a season from my home station to Clapham Junction.
Under 'route' it shows 'Not via London', no mention of travelling via Staines (I'm sure in the past, before current job, I've bought single / return tickets to Waterloo which have said 'via Staines')
I usually change at Clapham Junction, as the connection between Reading trains and the Twickenham - Kingston - Wimbledon trains is usually about minus 2 minutes or 28 minutes at Twickenham in each direction.
A while back, I tracked down the national fares manual online (can't find it now so not sure if it's still in the public domain) and I am sure that Guildford was shown as a permitted point (or some such - I can't remember the exact term) - and I have travelled via Guildford on a few occasions (when there's been a minor problem on the Windsor lines, and when there has been rugby at Twickenham) and the GW guards have not questioned it (not that this proves a lot)
I'm not sure that a journey via Ascot and Ash Vale would ever be quicker (except perhaps if there's engineering works) and while I seem to remember that Virginia Water - Weybridge was also an acceptable route, the interchange time at Virginia Water is usually a bit tight for comfort.