Thanks for getting in touch, we're sorry to hear that you haven't had much success. Cauliflower seeds struggle a bit with extreme heat so possibly the hot temperatures we've had may affect germination. We germination test all of our seeds and achieve at least 80-90% germination.
For successful germination, seeds need the correct levels of light, water, and heat. They're less likely to germinate if growing conditions are too hot or too cold or in soil that is too wet or too dry. Cauliflowers are a little trickier than cabbages and the other brassicas.
You could sow again now (September) and overwinter them, so all is not lost!
Here's a YouTube video which may help - https://youtu.be/-Y_-ucQly88?si=nT6kmiJsSyAoPirT