On the replacement tube, there is another loose bracket between the flex hose and the push in seal at the base, is this attached to anything? the part number of the replacement assembly is 07C 115 629D
You are certainly correct when you said its tight! After removing the air filter box I can see the bracket with the screw but its impossible to see the bottom end to locate the sump fitting. Can you get to the lower end of the dipstick tube by removing the lower engine protection shield?