I've passed all the info on to the garage and it appears they've done it all already, really stumped with this one and open to any suggestions :-)

"it’s already had a cleaner through it as one of first things we’ve done. The diff press sensor has been tested already ����*♂️ we’re going to double do everything sensor wise and also put another cleaner through ������*♂️"

Edit: just had a call, taking the DPF to get it cleaned properly as all the readings suggest it's that.