T.C ... I love reading about others peoples experience, especially from the likes of job riders ... what's the article you wrote about, can you point me to it ??
i'm also looking into advanced training having done the ROSPA advanced driving course I wanted to stay with ROSPA for bike training but from what I've read i'm looking at a lot of money for the course, (correct me if I'm wrong) and i'm not putting a value on the training you get I just cant afford the course the ROSPA way, so if I join an IAM club?? and train with IAM is it possible to do a cross over/ fill in course for a ROSPA test or is there no point to doing it like this .... ive been reading both of the books and their very similar .... may I ask your advice on this ....(soz for the hijack) cheerz....AL....
amphibianalf
Usually it is only the diploma course for instructors that is prohibitive as that is run centrally in Birmingham.
But to do train up to the advanced standard with a local group is usually a fraction of the cost of joining an IAM group.
If you look at the attached for example, and which also happens to be the group that I helped start 30+ years ago, the cost of joining, plus one on one training and other benefoits is £47.00 which also includes your first years annual subscription, + of course you get the opportunity to hear me dribble on about various topics by way of talks every so often as well 
https://www.roadartvg.org.uk/index.php/costs
The test costs £63 or £68 depending on your age
https://www.roadar.org.uk/riders/the-test.htm
But of course there is nothing to say that you have to take a test. Many are quite happy just to know that their standards have improved. So, in my opinion, costs are comparable with IAM, and depending on where you live, if you shop around, you may find local smaller groups charging less.
That said, if you go with an IAM group, there is nothing to prevent you doing the training and then doing whatever test you wish. Now that the IAM have their First and Masters, standards have improved substantially over the past couple of years and so they train to a standard rather than to pass a test. Doesn’t matter what book you read, there is only one that matters “Roadcraft” which both use as their bible,.
So the bottom line is, train to a standard rather than a badge, and your standards will be appropriate to either organisation.
Shop around for a group that suits your budget, but, RoSPA should be no more expensive than the IAM costs.
I should also add that you can apply for the test without the need to belong to a group. You apply independently and that is the same for both tests.
On the flip side, in all the tests I have conducted over the years which probably runs to a couple of thousand (including car test as I am a car examiner as well) I do not recall ever having awarded a gold to anyone who has not had training. I have awarded silver to a few self trained riders, but they were a long way off the gold standard, bearing in mind as you probably know, the benchmark test we ask ourselves before awarding gold is "Would this person acheive a Police class 1 with mininmal instruction? which I guess is also the same question applied to the IAM First and Masters as well.
But then, I have always been quite tight on awarding the gold grade 
Hope that helps?
Oh, and which article are you referring to? I have done a few?