Like the rest of the self-help industry, it's completely unregulated and there are tons of people offering quick fix solutions and "guaranteed results" for £1,000s.
The bad news is, for most guys who are consistently getting poor results with women, there is no magic pill, no one line, no one effective technique, that will make a hot girl jump into bed with you. It takes time, effort, practice, patience, commitment and motivation to improve any aspect of your life, and getting girls is no exception.
The GOOD news is, in amongst the many self-proclaimed gurus, mPUAs and dating coaches, there ARE guys who are not only consistently good at attracting and seducing women, but also very good at explaining how they do it, and how YOU can too. I know this is true because I've not only studied a lot of material, but I've also had the opportunity to meet many of them, and through doing so vastly improved my results.
The only way to check if investing in a product or training is right for you, is to search around amongst the companies and individuals, read their reviews, watch their videos, and see which guys seem like the kind of people you'd like to meet, and that have a style that fits your personality. Then contact them to discuss your particular issues, and see if they can give you some advice and guidance about which of their products or services might help you best.
The guys that have really influenced me a lot recently and helped me significantly improve my game are:
Sasha
http://www.sashapua.com/
Alan Roger Currie
http://modeone.net/home.html
David Shade
http://masterful-lover.com/cmd.php?af=1325438
Badboy
http://www.badboylifestyle.com/
David X
http://www.davidxdating.com/
But these guys may not necessarily be right for you personally. The important thing is to go out with an open (but still healthily sceptical) mind, and find the style and trainer that's right for you.