As someone from the UK, with friends who work as programmers in both the public and private sectors, I'm not sure what you're saying is true. It's definitely not highly paying to work for the government, although "relatively" may be doing the heavy lifting in that sentence.
I'm going off what I was told when I expressed surprise that such a good engineer would go for government work. Looking online it looks like they pay about median for a software engineer in London. And yeah, relatively here is basically meaning I was surprised you didn't have to take a pay cut to work for the government.
