one source is links such as those below, the other is the individual web site for each course. The problem is that the level of information provided varies enormously and can be out-of-date (especially green fees). You may get a scorecard but will rarely find a hole-by-hole guide - they want to sell that at the course.

www.englishgolf-courses.co.uk/
www.top100golfcourses.co.uk/
www.uk-golfguide.com/