My first lesson from hell

It had to happen sooner or later.  A lesson where the behaviour is out of line in a big way.  I've been given a third year class who are a supported set.  There are only twelve but the class divides up into a) super quiet and pretty keen students who have large learning difficulties such as dyslexia and b) super noisy and disruptive pupils, some of whom additionally have learning difficulties (but not all). It was the first time that anyone has said "No" to a request in my class (actually I think the actual word was "Nu'!"). No to turning round, no to taking their bags off the table, no to doing task a instead of (more difficult) task b; no to moving seats, no to leaving the room.  I was called 'pervy' by one pupil for giving them a writing task describing a room in their house (' what do you want to know about my bedroom for?" - even though they had a choice over which room to write about and she chose her bedroom).  Four pupils out of the nine who were there (was it really only four I ask myself?) talked over me, fought with each other, shouted out and paid little attention to anything I said.
There were circumstances that contributed to this crazy lesson:  a last minute room change due to exams (so id didn't have their jotters, have access to the computer to start with, or know where the punishment exercise sheets etc were), a cover teacher in with me they weren't expecting and their usual teacher not there; it was last period on Thursday and it was a windy day.  Two pupils had never met me before (they'd been off the last two lessons) and two had only had me once.  I'd already gone over my rules and expectations twice, so I did it very quickly again for the two who were off, but didn't really talk about sanctions / rewards.  
It was HORRIBLE!! The cover teacher was great and only stepped in twice when I'd told someone to move seat, or leave the room and then he bellowed at them to do as they were told (which they did). But I was fire-fighting the whole lesson. 
It led to some really good conversations about how to manage this kind of class.  First of all, I wasn't too hard on myself.  The cover teacher told me that his heart sank when he saw the class list and that I have 6/10 of the most difficult 3rd years in the one class.  Even their current teacher, who rules with a rod of iron and a shout that brings tears to MY eyes, admitted to me that she's had to have a good cry after lessons with this lot at times. I was glad to hear this, since that's exactly what I did when I got home to my mum who poured me a large glass of port and made the tea for me and the kids that evening, bless her.  
Here's what I plan to do on Monday in preparation:  

1. Introduce rewards - behaviour chart for positives, hard work, participation, insight, creativity etc
2. Go over sanctions:  1. warning  2. move seat (if appropriate) 3. punny - 100 words, upping to 200 if there is any; detention slip; out of class
3. Have punnys and detention slips already filled out, which will be put on their desks if they have to move; have a clear plan where they will work (and what work they'll do) if I send them out of the class
4. Practice my stern voice
5. Remember to speak quietly in the ear of people for things like bags on desks, phones out, etc so its not confrontational
6. GIVE 2 POSITIVE COMMENTS before I use a sanction.  "You listened well, which helped the class hear.  Well done."  "You gave a really good example there.  You helped the class learn there. Well done."
7. Learn a phrase "You talked over me. You disrupted the class. You broke a rule. That's a warning. That's a mark on the sheet."
8. Stock up on the port, just in case!