General diesel seaping down filler pipe

[uncle stewie]

We can smell diesel when we drive with the sunroof open...... on inspecting the engine compartment and underneath there is no sign of a leak but I have found diesel seaping down the outside of the filler pipe - between the filler cap and the main body of the tank - I assume that some sort of seal where the tank joins the filler pipe is seaping but how on earth do I get to see the joins if any and execute a repair? Hate the thought of prizing panels off inside the boot and still not finding out what's up. Stewie.