I planted two batches in September last year. One batch cropped in April as expected but I am STILL waiting for one batch (a different variety) to crop!
Like Newshoot says, some of mine did go immediately to seed when we had the hot weather in May, but I removed these plants and the remainder have done very little. I have recently given them a feed of tomato food to hopefully encourage them to produce spears.
I am frustrated by the sheer amount of space they are taking up - and no produce yet!
As shoot says, there is loads you can still plant.