Fuel Lines Slight leak

Hi All

I seem to have developed a small Leak on my TD4 03 97k the fuel pump has been replaced and the fuel filter was changed yesterday as part of a service (Thinking I may have had a small hole in it) when is spoke to my mechanic he recons the leak is below the fuel pump and nearer the fuel filter end., there is a small hose that goes from the pump to the filter, that looked as the possible offender.

So, Recent New Pump New filter

So what else could it be?

Overflow seal ?
Small fuel lin between pump and filter?

Any link to relevant diagrams and where to purchase ,the small fuel line would be appreciated.

Thank you in advance

FireOyster