A very credible result, Steve! Looks fantastic. All that cleaning would have pushed me over the edge though..
I've had good success in the past with grating or distorted speakers by carefully wedging pieces of foam between the metal frame and the back of the cone. It takes some experimenting to get it in just the right place.
My Hacker radio has worked for years with a chunk of washing up sponge poked in the speaker. It sounded horrible when I first got it. Give it a go- it might just work for you.
All the best
Nick