Pool of oil under my car

There is a small black pool of oil under my 2003 1.9jtd Doblo, I cannot see where it is coming from but this has happened before and it was the oil filter that went porous. The AA picked up the car and took it to the nearest fiat dealer as it was still under warranty. However now that the car is no longer under warranty I dont want it towed 120 miles away to a fiat garage if it is the oil filter that has gone porous again. But this is my problem where the hell is the oil filter to have a look at it too see if it is the same problem again. The pool is not getting any bigger so I am assuming that it has leaked out when the car has been hot and the oil is more fluid once cooled the drip of oil has stopped. Help

remove the undertray and take a look you will need a combination of sockets/spanners torx bits and a screwdriver and you can see the oil filter clearly on the underside, it may be something else its worth the effort to remove the cover so you can take a look!