Strong smell of fuel.

Daughters 04 TF - fitted used replacement fuel pump assembly using locking ring that came with the unit.
Seal looked good and all working OK except there is a strong smell of fuel. Rechecked fit. No sign of any leaks from fuel lines.
Are there different types of locking ring? Perhaps I should have used the original one from the car as it it didn’t smell before the replacement was fitted. Or any other ideas as to source of fuel vapour smell.  Seems to be strong with car just sitting not running?
Any ideas will be appreciated.

It could be the locking ring, but do check first that the fuel cap is not fitted upside down. There is a dimple and corresponding lump that is designed to ensure correct orientation, but it is possible to put the cap on the other way up and if that is done it will not seal properly. It was a common enough issue that MG issued a bulletin to their dealers about this being a source of fuel vapour smells in the cabin.