I'm looking for a cheaper way of making a day trip from Staines to Stratford upon Avon with a Family & Friends Railcard. The fares via Reading make it an expensive proposition.
No surprise there - the fare with route "via Oxford" are set by CrossCountry. They have been increasing regulated fares as much as they're permitted to each year since they got the franchise, so it's no wonder that the fares are expensive - they are only available on the basis of the old BR "Saver", which has almost always been on a higher pence-per-mile basis than Day Returns and other discounted tickets.
I discovered that a super off-peak day return from London to Stratford upon Avon (route Banbury)
I presume you mean the Super Off-Peak Return. Chiltern doesn't set any Super Off-Peak Day Returns - those are primarily the reserve of the south of London TOCs (SWR, GTR, SE), though a few other (primarily London commuter) TOCs offer them. But not Chiltern.
Agreed - this is perhaps to offset the fact that the Chiltern line is, by default, undeniably slower and less attractive than the alternative WCML, at least for travel for Leamington Spa, Birmingham and northwards.
However, would it be valid to start/stop/break at Staines, given that Staines is on a valid route between London and Reading?
Unfortunately not. The maps that set out this validity can be viewed
here. Combinations GC and WR+BB are permitted. You'll see that WR+BB lets you go via Reading, but unfortunately only if you travel on the GWML, not on any SWR services.
If anyone could help me with this (or suggest another way of getting cheaply to Stratford from Staines for the day) I would be incredibly grateful and very happy!
If you're travelling on a weekend, and want a flexible ticket, it's likely to be cheapest to split your tickets across London - using either a ticket to or from London Zone U1* to cover the cross-London transfer from Waterloo to Marylebone, or Oyster/contactless. Chiltern does offer Super Off-Peak Return tickets from Staines through to Stratford-u-A (in this case routed "via High Wycombe") but they are disproportionately more expensive than having a Weekend Super Off-Peak Day Return to/from London plus a Super Off-Peak Return from Marylebone to Stratford-u-A.
Alternatively, if you're prepared to tie yourself to a specific itinerary, Advance tickets (through from Staines to Stratford-u-A) can be very good value for money, but you have to buy them at least a few days, if not a week or two, in advance to get a reasonable (and worthwhile) price.
