Brassicas

I'm embarking on my 4th attempt to grow some decent winter veg other than leeks which I have no difficulty with. I have tenderly raised some brussel sprout and sprouting broccoli plants (about 12 of each) to set out and have constructed a formidable netting cage to keep out the dreaded cabbage whites, only trouble is I can't get inside it that easily without severe contortions but that aside if I plant them out in the next couple of weeks when will I get a picking? Also what's the minimum planting distances between plants/rows? because like everyone else I'm tight for space. Can you catch crop anything other than salad stuff between them? I've salad stuff coming out of my ears and I can't plant carrots because I've dug a load of compost folowing on from the potato harvest!