Is it too late to sow broccolli and cauliflower in the plot?

Im no expert but my method is stick it in and if it grows result if not try next year! My nursery is still selling cauli to plant so cant see why not. I have had my allot just over 2 yr now and the 1st year was a bit like yourself, find a space and plant something. If everything grows well and no diseases appear dont worry bout crop rotation till next yr and your sorted but if you plant potatoes, cabbages, tom etc in the same space too many yrs on the trot you may run into trouble. So straighten it all up then worry bout things like that for now find a space, plant and fingers crossed!!!

I've just sown my cauliflower for overwintering. (Winter Pilgrim).

I wouldn't grow them on the window sill, they don't like it too warm. This can lead to leginess & bolting.

The seeds I mentioned took just 3 days in the open, (one seed to a module), to emerge.

As I said in the last line of my post, they are outside, one seed to a module.

No need for slug protection, they are standing on the rough tarmac driveway which the slugs stay away from.