Try loosening the sensor pipe a bit mikey...it may allow the deltaP to read a bit lower and start a regen, I would cancel it after about 3 minutes, then ....wait 4 it to cool, hook up the pipe, and try again.
Just be careful, and have the garden hose ready!
Have you done a forced regen before? It's rather dramatic, hot, noisy, smoky, do it with the bonnet open.
Look at the other posters figures, 1250mbar would seem like a fault, as the diagnostics suggest.
I know you're a proper engineer, so this answer int for everyone, as if its really choked, you're in trouble if you don't notice the danger signs.