A pretty good write-up of the case! Hi, I’m Anthony Hogg. I’ve written about the case for about ten years. Your criticisms are on point. But I should point out that there are a few errors, namely: the inference that Manchester was a bishop at the time of the investigation (he was ordained in 1991), Lusia (real name: Jacqueline Cooper) is the vampire Manchester allegedly staked after 13 years, not the Highgate Vampire, which was staked ca. 1973. She was its victim.
Also, Lucy Westenra is not buried at Highgate Cemetery in the novel.
In the meantime, I thought you might be interested in our own investigation into the vampire claims, which reveals the impossibility of what Manchester alleges about the vampire’s presence at the cemetery: http://vamped.org/2015/02/27/5-reasons-why-a-wampyr-didnt-walk-in-highgate-cemetery/