Here's what Brooks' customer service told me:
"It is possible to make this conversion, in theory, but it is not that straight forward
You need all of these parts:-
BYB 299 Flyer Bracket & Coil Assy
BYB 274 Backplate Assy
BYB 298 Flyer Side Rod
BMP 183 x 2 Nut
BYB 702 x 6 Rivet"
Clearly not worth the effort, but I'm glad I asked and thanks again for the posts.
Rob