They had a South and South East split right from launch, though to begin with, Coast to Coast (in its initial 5.30 slot, incorporating ITN’s 545) also had a pan-regional segment - think at least some short bulletins were pan-regional as well.
Eventually, they were fully split - and down the line, TVS launched a short sub-opt for the Hannington transmitter - which was usually just a news round-up segment during Coast to Coast in the South. But they also tried some split non-news output (This Way Out - a weekly what’s on guide - apparently featured a Hannington opt)
The South East also did a similar news opt for viewers served by the Heathfield transmitter - albeit broadcast from Maidstone (much like how the Hannington opt came from one of the two Pres studios at Southampton)
Come 1993, the Hannington area was turned into a third sub-region by Meridian, who launched a full news service out of a studio in Newbury - the West edition of Meridian Tonight was later moved to Southampton c. 2002.
The Heathfield opt seemed to disappear after TVS closed - but apparently, there were plans to launch a fourth Meridian news sub-region for Sussex, to the extent that their Brighton bureau had a small studio and gallery installed (this according to one of their ex-engineers)
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That, as we know, failed to materialise, though I think there was another sub-region solely for advertising purposes.