Winter veg - misc advice

My first attempt at some winter veg this year in my garden raised beds.  Have some red russian kale, sprouts, cabbage, perp spinach, mizuna and Hilde winter lettuce.  Some questions:

- my brussels were in pots for ages whilst I waited for space.  Went in end August and are finally taking off.  What should they be looking like right now (never grown them before).  Theyre about 1.5 feet high, with a few layers of smallish leaves hanging out, and a mass of small leaves forming at top 

- when is it best to harvest the kale - when the leaves are biggest, smallest, somewhere in between?  I'll need to wait until the caterpillars go regardless - they've had a field day on 'em 

- got some winter lettuce & mizuna seedlings in.  Still v small but I reckon they should be fine.  Do i need to protect them from frost (cloche etc).  Bear in mind we get some pretty hard frosts up here by Nov / Dec.

Cheers

It's my first year so I'm no expert but my sprouts were planted on at the end of May. They're about 4ft tall and have well formed sprouts on lower part and newly formed towards the top.

I'm fighting off the caterpillars like mad and am still praying that nothing affects my harvest!

I'm sure someone more experienced will offer some advice.

I've tried some of my red kale. Took the new leaves from the top, which according to advice on packet, encourages more tender shoots to grow. They're about 3' tall.  I'll wait until later to really crop it, as it's covered in clouds of whitefly
I protect my winter lettuce with some net curtaining, worked last year, we had winter lettuce right through.......but we are blessed with warmer climes here
My sprouts are pretty big and I'm harvesting sprouts already, either to eat or for the freezer. There were some 'blown' ones to begin with but I took them off and gave them a good comfrey feed or two and they look good now.
Last year was a disaster for my brassica. All got eaten by pests or just didn't take off.
This year I was much more careful to net them with small mesh for butterflies and next I'm going to put stronger netting over for the winter to keep the pigeons off, hopefully
We are looking forward to PSB, red kale, savoy cabbage(not sure when to pick these), sprouts, and hopefully spring cabbage.
Sorry to natter on about brassica.....it's our 2nd year and this is the 1st season of any success with them.......still lots to learn though.  Cabbage family rules supreme