Garden Design courses

hello chaps
OK, so I'm signed up to study the RHS certificate at night school now, but I also want to study garden design specifically. I've had a mooch about on t'internet and had to have a lie down in a darkened room with a damp flannel on my head. Did ya know you can spend 7k on a course at the Chelsea Physic Garden?! NO, neither did I. The Asst. Est Mgr went a funny colour when I showed him the site. Poor love thought I was going to put him up chimneys to finance it!
So - looked at other options, and there are lots. Once again I'm looking to you guys for advice. What I don't want to do is invest in a course which has no credibility, or is a kinda "style over substance" thing.
I see this KLC outfit mentioned a lot in the back of gardening magazines, but my rampant cynicism thinks that if they have to advertise that much what does that say about them?

What does the collective wisdom of GC think of such courses, and does anyone have experience of them. Finally, does anyone have any recommendations on this?
Many thanks
lynne