The bonus co-ords need to be fiqured out using the musical instruments found in each cache. Make sure you make a note of which instrument was in which number cache! The route is mainly along footpaths but some caches are slightly off of these paths. This trail can be followed in a car.... but why would you want to do that? 
The Trail Bonus Cache is a music theme. Steve Barnett was born in wolverhampton in 1952 and went to Codsall High School as a boy, He then began his music career as an agent in London in 1970. Steve Barnett is now the Chairman & CEO of Capitol Music Group which includes artists such as The Beatles, Rod Stewart, Emeli Sande, Katy Perry, Mary J Blige, Neil Diamond and Naughty Boy. In his past Barnett represented artists such as Elton John, Black Sabbath, Deep Purple, AC/DC, Cyndi Lauper and Foreigner. Barnett also took a key role in marketing artists including Pearl Jam, Audioslave, Shakira, Jennifer Lopez, Franz Ferdinand, Modest Mouse, Good Charlotte and Natasha Bedingfield.
Each Geocache has a musical instrument inside which is to be used to find the bonus cache. I repeat Make sure you make a note of which instrument was in which number cache!