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Yep, get a tracksaw. And watch Peter Millard on YouTube for how to use it. e.g. https://www.youtube.com/watch?v=_8sagpnlF1Q
The MacAllister ones from Screwfix https://www.screwfix.com/p/mac-allister-msps1200-165mm-electric-plunge-saw-220-240v/274gf are extremely good for the money, and seem to be a rebadged version of the older Titan saw, as featured in Peter's videos. If that's the case then they are compatible with Makita and Festool track, should you want to buy longer lengths of rail.
This 100%.
@rogan
If it's a one-off and you're not planning on doing a lot of it, spending on tools is a waste. You have to learn to use the bloody things and that'll definitely come at the expense of wonky lines. Nice ply isn't the easiest to get a beautiful finish on at home. If you can order it pre-cut then you'll have none of the mess/faff/work for better results for, almost certainly, less than the cost of materials + tools.