Step one, after unscrewing the hinge and removing the keyboard, was to start sanding down the high gloss black paint. This is when I discovered that a) this is incredibly messy and gets black powder everywhere, and b) this is not a good thing to do when you have a gaping wound on your index finger.
Therefore I needed to wait until I could do the sanding outside, which needed daylight, which needed it to be the weekend. Luckily by this weekend, my cut had almost healed and just needs a token bandage on it to keep the skin flap from catching on things (ok, sorry, not trying to be gross, but you know what I mean if you have ever cut your fingers).
As part of Step one, I resurrected a vertical belt sander that I bought about 15 years ago, which has been languishing in the attic. As soon as I turned it on (outside on the patio) and held up the piano to the sanding belt, I remembered why it was no longer in use. The sanding belt (only 180 grit) basically ate the piano. In a split second, not only was the black gloss coating gone, but so was part of the piano. After recoiling and recovering, I realised that I now had no option but to grind off the rest of the black coating to try for an even result.
Then I sprayed it with white primer, having previously covered up the 'strings' with some card and masking tape, and gave it a base coat of Games Workshop Bleached Bone acrylic paint.
After the first coat of Bleached Bone, I removed the protective card so I could paint carefully down the inside around the 'string' area. It took about four coats to achieve an even result all over the piano.
I had previously photoshopped some toile paper to look a bit like the Lydia Pickett artwork. I'm not great on Photoshop, but I copied an image of toile from the internet, shrunk it down to approximately 1/24th scale, tiled it to make a bigger area of toile using copy/paste, then used the Photoshop colour management to lighten the green and to lay over a beige screen. I printed this on the colour printer at work, and then sealed it with some DecoArt multisealer. I then tried to channel Robin Betterley to cut out pieces of toile to decorate the piano.
The above is a picture after applying the toile paper, but before applying gloss varnish. I'm going to apply a few coats of gloss varnish to help it all blend together. It's still a bit crude (the strings aren't going to convince anybody) but I think it will look nice on the mezzanine until such time as I spot something better at a show. Not bad for $7 / £4 anyway.