Owners' usage patterns cause issues with DPFs, not specific models.

DSG transmissions are like marmite, all good or all bad - VW Group have made some dogs of DSGs but other versions are sound.

1.8 diesel ? Are you sure, I only thought it was with a 1.6 or 2.0 in diesel form

Correct, no 1.8 diesel..

And since the OP is considering the FR that kicks the 1.6 off the list, the FR is only available with the 2.0.

As for DSG problems the 2.0 has the much tougher wet clutch 6 speed box, we had one in a 2.0 Golf TDi at work as a pool car and that did 150,000 with no issues.

All diesels will suffer DPF issues if used inapropriately and these are not covered by any warranty.

The Leon is a great car, has the OP considered a 1.4 TSi 150 PS manual, its without doubt the pick of the range and probably the best car it its class.