Yellowy cauliflowers?

I think I'm right in say now would be a good time to harvest them if they've gone an off white-yellow colour ! I was told as they get towards that stage you can fold a leaf stem back over the florets to stop that happening -I've found to an extent it works.
Mine got to that point about 2-3 weeks back so I harvested them and planted some more that I'd had going from seed in the greenhouse.

As long as they're not to yellow you should be all right -mine were about the same as what your discribing and have been ok. Best to strip the florets off the storks and freeze them. Otherwise it's cauliflower cheese all week-lol

I was told that as soon as you can see the curd, it is time to cut it to eat, even if it is small still