Probably 6 to 8 inches away and bend them as they grow up your supports. 4 inches deep and then some mulch. As you are growing against a wall, I suggest that you dig down before planting and line the side of the wall with some heavy duty polythene to stop the roots from drying out when the foundations compete for the moisture.

Thank you

If you can I'd go out a bit further from the wall 12-18" if you can and then you wont need to line the wall side. If there are canes in the pot with the clematis lean them towards the supports. I have mine trained onto wires that stand a good 3 inches from the wall to allow air circulation around the back. the wires are twisted round metal eyes that are fastened to the wall.

in other areas of the garden they are up trellises.

welcome to GoY too :o)

Agree with Seaburngirl - it needs to be a foot away from any wall or fence as a minimum to avoid what's known as 'rain shadow', meaning any closer and it may not get sufficient moisture.

many thanks for all your expert opinions.
John