Hate to troll, but -
Â£4000 doesn't buy much of a superbike. Â£7-12000 will get you a mediocre stock BMW/Ducati. Some rice-rockets are slightly cheaper but lack most of the sex appeal.
I've had tons of women ask for comment positively on and/or ask for rides on my crappy $6500 Kawasaki rice-rocket and had a similarly positive response to the $3000 Vespa scooter I drove in college.
Guess showering helps?