I want to erect a fence along the garden wall but there are brick supports that petrude from the wall making it impossible to run the fence flush along the wall. How do I get round this problem?

I assume when you say brick supports, you mean piers, you cant remove these. Options are you could loose a bit of room and set the fence flush with piers or panel inbetween piers. You havent said how high the wall is, or how high the fence will be. Edit to your extra information, if your using 6ft wide panels cant you set your post out, so as they miss the piers, if so then fit some 8ft post in tight to wall, as you already have a 4ft wall then you only need 2ft panel with the bottom edge sitting level with the top of the wall, this will give you the 6ft and be cheaper.

Clad the peirs in the same material as the fence.

what kind of fence you nd to erect is closeboard with ur bowtop trelis bays on top of closeboard but most of all you should use cantrails as they are able to be cut down to suit the measurments oth brick peirs b and when fixining the post to the wall i wld use m10 ram bolts or studing and chem fix does this help

If your wall is straight and sound you could run a lower fence line along the top of your wall. Use 3 x 3 inch bolt down met posts to house your posts along the top of the wall. Then run your fence panels between the posts.