Just finished cleaning off the remains of the varnish/lacquer on the stock. It came off very easily, surprisingly so which may go some way to explaining the patchy appearance in the first place. Rather than risk damaging the checquering with mechanical cleaning I left it alone apart from cleaning it out with a mix used to clean antique wood. Most of the dirt lifted off, not perfect but adequate. The stock wood was very pale & I chose a yellowish spirit based stain to try & match the original colour. This stain has gone on evenly but darkened the wood a little more than I hoped based on how it looked on a hidden test area. However I think it will lighten a little when being finally flatted before re polishing.
Quite enjoying this mini project, it will be interesting to see how it shoots when it's all back together, looking forward to trying it out.