By john.burgess@granthamjournal.co.uk (John Burgess) Heavy leaf fall is making fishing tricky at the moment on many local fisheries, with some sections of lakes and many stretches of canal thick with floating debris. But although all this surface rubbish makes it difficult to present tackle properly, there are normally plenty of good fish lurking underneath it. That is what Journal angling correspondent Dave Coster discovered on a recent trip to the Fossdyke Canal, just outside Lincoln. Dave tends to target this venue at weekends, because it only takes 30 minutes from Grantham by car, whereas …