OP, I turned into my own private detective (with the help of a good friend) when my ex dumped my out of the blue and behaved very strangely. I don't think your PD has done all that a good job, but I support your use of one and in general I think its best to do due diligence on any man you get involved with, in whatever legal way you can.
Are the marriage registers in England and Wales public? I found out my ex was married on the public register of marriages in Scotland.
It was actually really difficult to even find out that the reason I had been dumped was because he was getting married. I had no idea; it was a ldr and I thought a committed 2 year relationship, I had just found a job in the city he lived. I had confided in a friend who knew my ex through a mutual hobby and she was friends on Facebook with another woman who also did the hobby. That other woman posted photos of his wedding, along with the first name of his new wife.
Because his bride had an unusual, foreign first name, we tried to find her on FB. It turned out that she has no social media presence whatsoever (I actually suspect he has married someone without social media deliberately). So we became even more intrigued. It was only a matter of waiting for the public register of marriages to be published and there was his wedding listed. We think his new wife didn't have an internet presence because she was pre-FB generation; he is 41 and she is nearly 60...
Nothing surprises me now about the lies men will tell in order to get sex or lead a double life. I actually knew my ex through a completely different hobby and I had no idea that he had a secret life going on. I also found out that he had cheated with me with another woman I vaguely knew in the run up to his wedding, and with a former good friend a few years earlier when we had gone out for a few months, who had then dropped me.
I'm sure theres lots more still that I don't know, but my point is that you shouldn't feel ashamed or embarrassed that you sought out the truth about this man. Its the person leading the double life who should be ashamed, and it is a really good idea to find out who someone really is.