I think women who would immediately write him off solely because he 'only' earns 60K without getting to know him first probably aren't the sort of people a decent, nice guy wants to me. But I think that age is a tricky age. Many women, even in London, have a long-term partner/marriage by 40, but they aren't necessarily old enough yet to be divorcing and back to dating. It's likely he's dealing with a small pool of available women (some of whom frankly might be single for good reasons - because they are foolishly picky, or have hang ups about things like money, or just suck at relationships).
I also have a really lovely friend, who is a bit older than that now (mid 40s), and single. He also really struggled with why women didn't seem that into him. He is really nice, though not 'hot' by traditional standards (I would class him more as geeky), but not unattractive either. His problem unfortunately was that he generally was attracted to women in their 20s, which was totally the wrong demographic for him. Girls in their 20s aren't interested in financially stable, homeowning men in their 40s unless they are rich and hot (he was certainly not 'rich' though had a good career and a nice home, definitely wasn't 'hot'). Unfortunately, he lost a lot of time chasing the wrong thing at the wrong time. And when he did meet women his own age, I think he was a bit awkward about it and sent weird signals and like you said didn't pick up on the right ones. I think if he could have gotten to know people a bit better before dating them, he wouldn't have been so awkward, but he did a lot of online dating and it was like date after date after date, and none of them really gave him a chance (probably because they were also in their 40s and a bit awkward like he was).
But no, I don't think most women would be turned off by a man with a career and a 60K salary (even in London, in my field that would be pretty good) and his own home. I think most wouldn't want some slacker who would expect to be financially supported by them. I expect it's more a matter of how he is around women and also frankly the pool of women is getting a bit smaller in your 40s, so it's just harder.