The Plan is that I don't want to do any marking with a pencil or pen that might need washing out. I do want to sew around templates to get the patterns evenly placed and because the white borders & sashing don't have seams where I need them for lining the templates up on (ie down the centre line of the sashing) I am planning on putting a line of masking tape down the middle, sew with the clear thread along the edge of the masking tape, which can then be lifted off in short order. Then I will divide the long sections into shorter sections, at right angles, again with masking tape and stitch along the edge of it and lift off the tape. This will give me a grid for locating the templates on that won't disappear and will take being scrunched up under my domestic sewing machine.
Yes I will have to do a load of unpicking at the end, but that doesn't bother me if it means that my quilting design is nicely placed and I can avoid fmq
PS I plan on making my templates out of sandpaper again, it works great.