It all depends on the car, some Peugeots will regen happily on local roads and no high speed motoring is required, providing the additive tank is not left to go empty and the other components are maintained, such as glow plugs.
Some people and even mechanics think and say that glow plugs are never used and need never be replaced, which is why they're sometimes in hard to reach places in the engine bay. This is complete rubbish. Their entire reasoning is based on the fact the glow plug light doesn't come on unless its really cold.
They don't seem to know or understand or care about post-heating or the use of the plugs in a regen.
The trouble with the AA is they're pretty generic when it comes to vehicles.
Its certainly the case when they go out to a breakdown, stick on the code reader and just guess at what the fault might be based on the fault code.
They've misdiagnosed three of my customer's cars - told two that they needed two high pressure fuel pumps when they needed a fuel filter or a clean of the lift pump, and on another told him that his entire ABS system was faulty and needed a new ABS ECU when it was a faulty ABS sensor on one of the rear wheels.
As for DPF prices, have a look here:http://www.cats2u.co.uk/
Much cheaper than the dealers, and no less quality as they sell OEM and type approved.