Believe it or not, large stones suitable for rock gardens are difficult to find in the Clyde area. There are a few quarries which supply stone mainly grey whinstone, but it is crushed to about 15mm for driveways. It may be that a quarry could supply large stones but it would probably need heavy machinery to move them into position on site.
Other sources are some garden centres and builders merchants who can supply various types of suitable stone in large non-returnable bags.
If I remember correctly, the price is prohibitive. One stone weighing about 10kg could be £10.
The method I used was to go out looking for suitable stone and carry it back home in the car. One car and one back wrecked !
You could always try the yellow pages for local demolition contractors and see if they have any old buildings being demolished in the area.
They have to pay landfill tax to dump the stone so may be glad to get rid of it cheaply.
As to designers, sorry I have no idea. The fun of producing a garden is that it is YOUR design. Just look at books, magazines, web sites and visit gardens - big and small. If you see anything you like incorporate it into your own design.
I forgot to mention Cardwell nursery at Lunderstone Bay, Gourock, maybe they could help.
