Grading issue - help required

Anyone have any suggestion as to how to add the same vingette or other effect to a selection of clips - other than rendering out a sequence and adding a vingette to the rendered clip?

There are many options. You can for example add the clips to a group and grade the whole group. Another option is to add an Adjustment Clip above the clips you want to affect, then grade the adjustment clip.

Or make a preset

Or make a preset

This is perfectly fine. Do note, if you decide to later adjust the vignette, you will need to do a bunch of work.

Group grades and adjustment clips will make en-masse changes much easier if that is desired.