DPF cracked?

My son has a 2013 Octavia 3 purchased from a dealer about 11 months ago.

The dealer has proved deeply untrustworthy and has lied about many things. That’s another story. In spite of this the car has mostly performed ok.

However, with MoT looming he’s mentioned again that the check engine light is on. Code is PO401, insufficient EGR flow. Car drives fine so I’m suspecting that the EGR filter in the LP circuit is blocked. This in turn likely means that the the DPF is cracked - a theory supported by the sooty tailpipe 🙁

We could clean or replace the filter pipe, which will probably keep the light off briefly (until it clogs again), but this is probably pointless as even if the MoT tester doesn’t spot the sooty tailpipe, the machine will spot excessive particulates?

Anyone else travelled this way? I’m thinking aftermarket DPF replacement and a through washout of the filter pipe is the budget option. Looks like genuine parts exceed the value of the car even before fitting!

Thanks

Nick