That's pretty effective Braz, thanks. I actually found some small plastic sleeves in my junk box last night. No idea where they're from but they might prove useful if a can find something of suitable diameter to locate them on.
My idea for the baffle vanes was a no-go; I picked up some pound shop screwdriver bits thinking that the wide flat headed ones would work, but they don't. The baby bottle heat shield idea didn't work either as the bottles were too short. The main engines donor bottles are surprisingly thick plastic too, making cutting it interesting. I'm working on a test engine first as that will then set the length of the main body.