My last years Tigerella tomatoes are still growing, flowering and ripening fruit, although the plants look a little bit the worse for wear now.
They are growing in my unheated conservatory where the night temperatures hover around 10c and mid-day temps of between 20c & 25c depending on the sunshine (or lack of)
They are growing in a commercial hydroponics unit which has a small aquarium heater which keeps the circulating water at a steady 21c. So it seems that as long as you keep the roots warm the air temperature doesn't matter so much as long as it doesn't freeze.
Anyway, the tomatoes are remarkably tasty still although not up to summer time standards but far superior to shop bought ones, although I must admit I haven't bought any in a shop for many a year so my memory could be a bit naff.

They are ripening just fast enough for me to have a cheese and tomato sandwich for my lunch every day.
I see from my diary that these plants were sown on the 9th March 2009, so I wonder if the will make it to their "birthday".