When I had some paintwork done on my MX5 2003 the body shop said that they would need to ring Mazda (assume a Mazda dealer) to get the paint code. I’m guessing but maybe Mazda can confirm this using the vin or other ID numbers on the car. Might be worth a try.
I’ve had reasonable results with the Upol paints from Amazon on a couple of different cars, but as with all these things, test it first like you did with the Wilko mix. Here is a link to a kit (they also do single cans of the colour)
Looking like a dodgy mix from Wilco, I actually bought two cans, tried the second one earlier and it looks much closer. Will see how it looks when properly dry and with clearcoat, fingers crossed!