[Slartibartfast]

i think he's only joking about starting to fancy women. Derek does this all the time, he uses hyperbole to show how frustrated or how strongly he feels about something. He purposely over exaggerates things and says something ridiculous (like he's starting to fancy women, or Science almost makes him want to join the BNP) but he clearly doesn't mean it. By saying something totally unbelievable he emphasises whatever the problem is.