I think you need to accept that the realities of computer-based journey planning does not simply end at what is explicitly stated in public-facing documents, and that some data that you realistically would need to use for making these tickets function within a journey planner (such as interavailability!) simply does not exist in any industry-wide distributable electronic format.
Farringdon not being included within Zone U1 is obviously garbage because, in any common sense of the meaning "Zone 1", it quite plainly is. Plus this data obviously can't be used for everything because not all LU locations are contained within RDG data, let alone being associated with the correct Zonal NLC.
The public facing documents are slient on the matter of routing of U-zone tickets, and also some other tickets like Boundary Zone tickets. In particular, it is silent on the OP's initial matter trying to change from train to tube at Waterloo East. A train-tube ticket combined a train ticket and a tube ticket onto one single piece of paper, therefore there must be an interchange station from the train to the tube, yet I can't find any public facing documents saying that which station is the interchange, and the Routeing Guide does not deal with any tube journeys at all.
The only document I can find about the routing of such tickets is RSPS5047 which provides the technical specification of journey planners, and according to that technical specification, the journey should not be validated by a journey planner, solely because Farringdon "does not belong in Zone U1 according to the data".
There is an
old thread discussing the validity of a Witham - Zone U23 ticket on a route via Stratford - Willesden Junction - West Brompton where opinions were divided as well.
One said that:
The validity of that ticket is undefined. I believe the late Manual, for the reverse ticket, said that travel was allowed by LU within the relevant zones to any NR railhead, from where you could take any permitted route from the latter station to the destination.
If this is the case, OP's ticket would then be valid because OP is following a permitted route from the origin to Waterloo East. We are now arguing why we can't choose "Waterloo East" as the railhead.
Another said that:
Good luck getting far with that interpretation.
--- old post above --- --- new post below ---
In fact, the interchange station can be determined in most cases, but no, the information is not very clearly stated in the public domain, nor in internal documents, but it can be determined.
In this case, the £30.10 fare is for interchange at Stratford, and possibly at other stations, but definitely not at West Brompton.
without giving any further details how the interchange station is determined (the whole point of this thread), and most importantly, why not at West Brompton.
Another started to quote interavailability (note that the quote text below is now outdated - the current knowledge base specify the interavailability on this route is only for LU/DLR issued tickets, not National Rail issued tickets):
Stratford-Richmond (North London Line) and Willesden Junction-Clapham Junction (West London Line) are both inter-available routes for NR and LUL tickets (Source: iKB, London section).
The £30.10 Off Peak Return from Witham to Zone U23 is the £26.90 Off Peak Return to Stratford with a Zone U23 return add-on (£1.60 each way), as noted in iKB (London section) which is then used on the inter-available routes between Stratford and West Brompton (North London Line to Willesden Junction, change for West London Line).
And another
old thread on this very topic as well, where someone replied
If it was a U12 ticket I believe the U-zone validity could already be considered to have started at West Hampstead Thameslink as this is where the interavailability starts. Not sure what the point of the question is though?
without a definite conclusion, and the answer to this will have an effect if I can break my journey or not at Kentish Town holding a ticket from St Albans to Zone U12, intending to travel to Stockwell.
So now there are at least 3 versions of saying:
1. The U-zone validity starts at the moment interavailability is entered.
2. The U-zone validity starts at the departure from the final London terminal.
3. The U-zone validity starts only after changing to the tube, at any station within the covered zones a passenger wish to choose.
I will be grateful if anyone can find me a document supporting which of the above is fact, as I use a lot of U-zone tickets to break journeys at Farringdon where my office is, and need a concrete answer, supported by official documents, if Farringdon can be considered as the tube-train interchange (hence a break of journey is allowed) or if the rail validity does not cover Farringdon at all on my chosen route (hence a break of journey is not allowed).