Regarding things to ask at your appointment....

Not sure if anyone mentioned the valuable information that is at the top of the page in the little 'stickie' section.....
Scroll through the posts up there and you'll run across one with the most frequently asked questions, and there's a website you can click on that really explains alot about the SCS.

Hopefully the SCS will cover the sciatica pain that haunts your leg....they have high success rates for nerve pain/radiculopathy in legs and feet....
As far as the back pain....that'll probably be a 50/50......I know that they will be able to set a program for you that covers the lower back area, but whether or not it helps with the failed back syndrome, not sure.

One important thing you may want to get clarity on is which type of lead placement your Dr is wanting to do. The percutaneous leads are placed under the skin and are anchored into the 'dura' (meaty area).....this is a much simpler procedure, however the risk of lead migration or pulling the leads out of place runs higher than if they do the more involved type of lead placement, which is called the laminectomy. This type of surgery has to be done by a neurosurgeon (here in USA, not sure about UK) and it requires removing a small segment of bone from your spine to place the leads through.
Don't let that freak you out tho. MANY here have had it done that way and it pays off in the long run because there is a much lower risk of your leads moving, especially since you are still young (you and I are almost the same age and we ARE young! ), so if you plan on being somewhat active, this is a good way to go.
I myself have the percutaneous lead placement and am doing ok with it. I'm getting a good 75% coverage in the legs (burning neuropathy).....but I am having some lower back issues and recently had xrays to see if we can tell what's going on. Haven't heard back yet.

So, try to find out which type of procedure they are wanting to do....
Percutaneous or Laminectomy.

Hopefully you'll be able to cut down that list of meds you are on, since many of them aren't helping you.

Again, check out the 'stickies' at top of page.......lots of good stuff up there.
And there is a good thread regarding the Psyche evaluation somewhere down the line .......just scroll through all the posts and you'll run across it. Lots of folks put in their 2 cents and it really isn't anything to 'worry' about. It's mainly for the sake of your insurance company. This is a very high dollar procedure and they want to make sure you don't have unrealistic expectations of what the SCS can do for you.
Some people become very intimidated by having to get the evaluation, but it has nothing to do with seeing if you are 'crazy' .....

Hope this helps.
I'm excited for you.
Rae