Tony, If you don't get your registration number prior to the deadline it will be "illegal" for the waste collection companies to remove your waste. Any of these companies that you currently use can do the paperwork for you but you will pay a premium on top of the £28, you could do it yourself online for £18 (I think it's £18)
We have used Cleanaway for the last three years and have just ended our contract with them this month, all they have to do is empty the skip every two weeks but you would think it was rocket science they way they carry on.
If you already have a skip you should have been informed what you are allowed to put in it.
For the others that use Safety Kleen, how does your monthly subscription work ? and what do you get for it ? we use them but pay seperately for each waste product ie oil filters, anti-freeze, contaminated fuel etc