The link below goes to an interactive map of Surrey. From the menu on the right you can select the bridleway and byway boxes and identify bridleways and byways (by their number) that are either blocked or are overgrown to such an extent that cycling along them is not possible without accumulating extensive cuts and stings.
I report the poor condition of the bridleways to Surrey every year and they do eventually take action. Please report any legal off road route that becomes impassable or dangerous to cycle on.
http://www.surreycc.gov.uk/maps/surrey-interactive-map