Totally agree with pursuing a statement. I do regret (do to other circumstances at the time) not having had time or energy to challenge the refusal to assess ds (I made the application a few weeks before I deregistered to HE). Unfortunately his deterioration was so rapid that we were left with little choice but to remove him for his own safety, but I did struggle for a long while with wanting to keep him there to secure a statement. It just wasn't possible any more.
Mind you, in my LEA statements aren't worth much, legal document or no. There are several children I'm aware of who aren't getting a fraction of the provision they should have, despite very carefully worded statements and all best efforts by the parents, and are suffering as a result.
Bear in mind though, that it is possible to have a child assessed and issued with a statement whilst being home educated. The LEA may say they'd want him in school first and to complete a couple of rounds of IEP, but it's not necessary. I know of several HE parents who've successfully had their child assessed and got the statement needed for them to return to school.
I rather get the impression that your LEA is very similar to mine, and you'll have to decide for yourself whether it's worth challenging them. It could be a very long battle if they're that reluctant to help, and you could come away with very little. How well can your son cope with what he has at present? He may have a certain level of difficulty that you can all tolerate for the time being and you might feel it's worth continuing - again, it's your call. The extent of my son's problems was such that we couldn't wait any longer and we had to act hastily, but that's not the case for everybody.
I agree that a good school could make all the difference but the problem is in finding one. If negative attitudes are pervasive throughout your LEA then perhaps support is being withheld from higher up the scale than teachers and Heads. You might at times find you have a very supportive teacher or TA but that their hands are tied by superiors. Not only is that frustrating but it doesn't help your son.
When you say there is no group locally, do you mean HE or AS support? If it's HE you might want to look deeper - often groups aren't visible unless you're part of them. Have you tried joining HE Special? You could ask for contacts on there, but beware - there are some militant anti-school folk and a lot of politics in the HE community just now. It's a very sensitive area. If it's AS support ask at GP surgery or Barnardo's if you have one locally.
I agree it's best to get first-hand experiences before you make a decision, but do bear in mind that circumstances can change. When my son transferred schools it was on the basis of other parents' glowing recommendations and the new school was widely regarded as the place to be for children with ds's needs. I visited several times, got all the right answers and the right vibe. It seemed ideal. But within a year the place was falling apart, its reputation in tatters, staff leaving left right and centre and it's marked for closure in 2010. Things change. You might find what seems to be the ideal school but it might not stay that way. I certainly don't want to be alarmist but it's important to be armed with all possibilities before you make your informed decision.
The best of luck, whatever you decide, and I look forward to hearing about your progress.