Stopping your veges from going to seed is all about planting at the right time of the year. You need to plant when the temperature is relatively stable. For example, if you plant during the middle of winter, the season quickly turns to spring, the soil temperature increases quite rapidly and your veges go to seed. This is a common problem with barassicas (broccoli, cauliflower, cabbage etc) and happens with the changing of the season. To help eliminate this problem plant your seedlings at the start of a season as opposed to half-way through or closer to the end.
You may also want to try eating your vegetables sooner. When veges are left maturing for too long, they also go to seed. Awapuni has developed a great way to avoid having too many veges maturing in your garden at the same time. They now offer bundles of various veges that you can plant every four to six weeks. This allows you to have a constant supply of veges throughout the season without them maturing all at the same time and going to seed.