Hello again, It's unfortunate that your mini dealer has no idea. They are supposed to be trained and current with this technology. It ****es me off when dealers and workshops are like this.
Eventually you will need to replace the DPF, it won't regenerate for ever. Although they do have a reasonably good life span (usually approx 10 yrs) every item is different and if there is a problem elsewhere with your vehicle, it maybe causing your DPF to block prematurely.
Oh by the way, when i meant sit any wait i was referring to leaving it sit with the engine running. There should be a button or switch to activate it, to tell it to do the regeneration. But as i said earlier, it may not be this "type" of system.
You really need to find a new service/workshop, sound like these guys are either useless or out to make a quick buck.
All mini workshops have the ability to hook a diagnostic computer to your car. It will tell them if anything is wrong, what to replace and any other pertinent info.
Hope you sort this out.