This scheme is usually defined as Silver (11) and Fluorescent Fire Orange (209). You need to be patient with the Fire Orange as it is partially translucent so you may want to put a solid Orange underneath (though the Humbrol Gloss Orange (18) can also be a pain, at least in Acrylic). Reds and Yellows are notoriously lacking in opacity and not just Humbrol. I have done the Vampire is this scheme and my son the Gnat.
The Orange does work over a white primer tolerably well, the unevenness matches some photos of the era - and a little on the rear fuselage of yours, but you will need quite a few coats which leads to a step at the boundary with the silver. I don't know how the enamels go but I had quite a faff when using gloss white to try and over come opacity issues with acrylic.
You can buy decal sets of individual letters and numbers for the serials but I am not sure if you will be able to get the quarters square badge - you may need to self print that.