Briantist: Arqiva's Reference Offer for Local TV says that the chosen antenna design for Waltham is 'Crossed Logs @ 100 degrees - 4 Tiers', at 157m above ground level, on a bearing of 40°. It does seem that this is intentional.
We shouldn't forget that the multiplex will also carry two more channels - perhaps there was a desire here to try to cover the East of England at least a bit, since Tacolneston will mainly transmit to its north-east, and Madingley to its east (you haven't updated the Madingley page with these details). Sandy Heath is in the Reference Offer - aerials pointing to the west - but the Bedford licence hasn't been advertised, as far as I know.
An aggregate map showing where there are holes in the overall coverage would be interesting, for the two services that Comux are allowed to run.
Help! my Post Code is pa16 7py, Greenock opposite RosneathTransmitter. My wife has this notion to watch STVGlasgow but unfortunately it is not available to us. I believe people on the Blackhill Transmitter can. Is it possible to manually retune channel 25, is so what is the frequency? I have looked but no can find.