I'm one of the Solicitors at SEN Legal (and don't tend to read the SEN bits on Mumsnet as after a day at work, it's quite nice to read about about something other than children with complex needs and Local Authorities which are failing to support them effectively).
The law relating to children with special educational needs is a specialist area, it's not something very many lawyers deal with (indeed, I have had other lawyers as my clients). So, in looking for someone to deal with an SEN matter, whether you come in our direction or not, you really ought to be looking at the specialist firms in the field.
If you don't have good personal recommendations, then Chambers and Partners and the Legal 500 are good places to go next. Given the specialism of the field, when you're looking for an SEN lawyer, you're unlikely to have a firm that is geographically close to you. As a practice, we take work from all over England and Wales and we do most of our work by telephone and email. [Scotland and Northern Ireland have different statutory regimes]. If face to face meetings are important to you then ask your potential lawyers how they would arrange these.
There are also some very well respected charities and lay representatives who assist parents who are not in a position to instruct lawyers, but unfortunately the quality does vary (there have been a couple of cases recently where we have been brought into a case that was mismanaged by a lay representative). It's always much more expensive to sort out something that is in a mess than it is where a competent lawyer has been instructed from the beginning.
There's always a cost benefit analysis involved in working out when and where to spend money when dealing with a child with SEN - is it better to spend money now or wait till, say, secondary transfer or to not take legal action at all but put in place therapy provision privately and the cost of any legal work needs to be factored into the overall calculations you make.
The starting point in considering any case is always looking at the paperwork in full; it is not possible to provide sound professional advice when you've got a small excerpt of paperwork and you run the risk of saying something that is legally wrong, because you've seen another document that impacts upon the answer. It is not unknown for lets say, a parent to be unable to tell the difference between a proposed and a final statement and that sort of thing matters a lot in working out what advice to give.
Lawyers are also people too:) I do think it's reasonable to say that those of us who work in this field get a great deal of satisfaction out of helping parents and children into appropriate provision. It's very nice for us when we get to see the eventual results, some years after we've helped a family and they come back to us and tell us about the progress their child has made.