I recall that the Spectrum version did have ripply suns, but I'll have to go and check.
If they did it was only down to aliasing artefacts! The BBC version definitely did this trick, though. It looks as though what Braben and Bell did was to simply add a random pixel or two to each of the horizontal lines that made up the sun's disc, or possibly just move the x origin of the line by a couple of pixels. Either way the result was a sun that rippled at its left and right edges, but not top and bottom. The Beeb was the only 8-bit machine I saw do this, so I'm guessing the processor overhead was too much for the others.
For anyone who hasn't seen it there's a shot of the sun rippling
here (11m29s for anyone whose YouTube client doesn't auto-skip). It's a simple but clever effect. I remember being quite blown away when I first saw it.
One final oddity with the Spectrum version that I've never seen verified anywhere but I swear it's true; the two sides of the 48K cassette had two slightly different variants of the game even though the sides were labelled exactly the same.
On one side the enemy ships were the Cobra, Asp, Fer-de-lance, Thargoid/Thargon, Sidewinder, Krait and Viper. On the other side the Krait had been replaced with the Adder. The key difference was that while the Krait was faster, the Adder carried missiles. So the key was to always load the game from the Krait side until you could afford an ECM, then switch to the Adders which were slower and awarded extra kills if you shot their missiles. A sort of early mode switching to minimise risk and increase profit, if you can imagine such a thing
I clearly remember putting red and yellow stickers on my cassette to remind me which side not to load until I had an ECM
The World Of Spectrum archive contains versions of the original 48K release (with Adders) and the Joystick Club version (with Kraits) which does at least demonstrate there were two versions of the 48K code. But every time I've brought this up in the past I seem to be the only one who remembers having both versions on the same cassette.