The reality in the UK is that the freeview (OTA) lineup for a postal code is not always correct for actual viewing. This can be due to incorrect data (which could be fixed), but can also be down to the realities of signal propagation, or the choice by some (especially near the overlaps) to choose a different transmitter.
I do not consider the (kludgy, likely necessary, but apparently reactionary) /transmitters solution to be a good long term solution unless you are going to expand that to ALL countries, including the US and let people pick and choose their transmitters(*). GBR is a very special location for historical reasons (i.e. BBC) in how they have provided DVB-T transmissions and transmitter locations.
There are a couple of obvious ways to address this with the existing API structure.
* Require the users to open tickets to request the adding all of the freeview transmitters they want to use for each and every postal code (which is sort of equivalent to those in the US that are in dual "fringe" areas, but apparently in the UK the overlap is much more common due to the heavy coverage for all locations). From previous interactions, some people can see 2, 3, or even 4 different transmitters (and sometimes choose which to select based on the "local" news due to their historical/family interests).
* Add in all the freeview transmitters to all UK lineups, and let the user decide which they are going to use. In the UK, knowing your transmitter is almost second nature I have been told (at least for a lot of people who use software that needs guide data).
* Provide a new "region" (somewhat equivalent to the ZZZ global satellite, but perhaps GBR/Freeview?) which has a list of all UK freeview transmitters. This preserves the headend selection process.
* Expand /transmitters to all countries, including the US.
* Something entirely different (API 201607xx?)
* Do nothing.
I recognize that this is a long term consideration, and nothing will happen quickly. Thanks for the considerations.
(*) Which is likely to result in usage other than what you would prefer to see.