Fuel line leak Mercedes W124 C124 E220 M111.960

Relpaced the filter only to find that the compression fitting was leaking.Was adviced to replace the copper washer, filter or the fuel hose (feed line to filter).
Prices vary between 15 to 70 £ for the part "A 1244708075" plus postage.Trying to keep the spending under control as I will have loads of parts to replace.