Hi Hobbit the easy one first - taking in a friend - you'll have to ask your mediator and be prepared that if you take in a friend, then he can too! Personally I don't think it's a good idea but i understand you want the support. Perhaps you could arrive with a friend and they could wait while you're in the meeting?
Have you had your initial assessment meeting yet? This is where you voice all you concerns - good to make a list for that. EG one of my concerns was that we would agree something and then once he took the agreement to his solicitor he would say no (being the sort of sol he is)
The first question we were each asked at our first joint meeting was what we expected to get out of mediation. My honest answer was to be able to move on. In hindsight it was probably not a good thing to say as it's in his make-up to try to prevent that happening and I shouldn't have voiced it - stupid me I should have known better!
I think you have to go into mediation initially with an open mind to be directed by the mediator. Because I've already done a year of solicitors and also seen a barrister I had a clear plan - in fact I already had a spreadsheet neatly typed out, even though I didn't have any up to date details of his finances.
The mediator, I stress, cannot give advice, rather direction.
The starting point, after you've aired all your "petty" little grievances (which wastes time and money) is to have all your income and expenses compared and work out who needs what to live on. At the end of the day, everything else laid aside, it comes down to reasonable needs.
So for example, (and as you have DC over 18 like mine will be) is it reasonable that you should have a larger house as they might not be able to get a job for a while and will need support. Should he pay maintenance for a DC at uni if his income is bigger? Should non-matrimonial assets be "ringfenced" (kept out of the pot) if there is enough in the pot to meet both parties needs? What is both of your capacity to get a mortgage?
Don't know if you've seen the link re spousal maintenance, but if you're expecting to claim it for the foreseeable, it looks like that will be knocked on the head and you would only get it till you can get back on your feet/get retrained to earn yourself - a few years. I'm not claiming it.
All our situation are different and you would do well to get some sort of advice before you start.
Oh - and there are references made to what might happen in court. Have You seen Section 25 of the Matrimonial Causes Act? This is the basis by which settlements are made but not set in stone.
xx