I can tell you what I (think I) remember - but it's all so long ago... Someone else will have to supply dates.
They were an item for several years. (I'm sure 5 years was mentioned but...) Possibly before John (Tom's elder brother) died, but certainly after. Tom took over John's pig business and buried his grief in crazy ambition. Kirsty was extremely supportive; half her life in the burger van and half at the kitchen table with Pat. She was very much a member of the family and the assumed Mrs Tom.
You may remember when GM crops became an issue in the country. This was reflected in Ambridge when a neighbouring farm started trialling GM. Tom was incensed, lots of protest, arrest, trial. Not guilty.
He got a deal with a big supermarket. Meetings with the buyer (?) Woman in a suit. Who strung him along for business purposes. Fling. Eventually, guiltily arranged to take K out to very posh restaurant to talk. She was all excited, certain a diamond would be involved. He dumped her at the table. It was awful.
So this current story is .... poo frankly.
Feel free to correct all my inevitable inaccuracies.