DPF Differential Pressure Sensor

Hi everyone, I was hoping some kind people here might be able to giver me some advice. I have a 2011MY SD4 Auto HSE. For a few weeks I had a reduced engine performance message come up on the display and the car would not rev very high, under normal driving. Interestingly if you floored it it would go quite normally, now the yellow EML light has come on. I have just read the codes and it has two, P244A & P2456. Google searches have lead me to to look at the two hoses by the exhaust to see if they are perished, they are both fine. There appear top be quite few DPF pressure sensors for sale on eBay and i wondered if anybody knew if this was a recurrent problem on these cars and should i change that. Any ideas would be gratefully received.