Yes, this is a perennial problem for me in Malaga and the ITV (MOT) inspector actually failed my Modus for it. It had been left outside for 14 months while Covid kept me in UK, plus the time I'd been parking and driving it outside since the last buff. Last time was just the "Formula 1" cream, which was ok. This time, I used the 12V buffer (not as good as my UK DA, but I don't have easy mains access here) with a medium compound x2, then the Formula 1 (which supposedly has a UV protector). Huge improvement and it passed easily. 20 minute job, which I could have done while waiting to be called up for my inspection but I didn't think the yellowing was that bad. I'm fine with doing that once a year if needs be.