Jabbastabba

Hi Guys, I have a is 220d 2007 with approx 45000 on the clock, always been serviced using a Lexus garage. The check vsc, traction control and engine mgmt light came on last Monday. Managed to get it to the local garage who think that it could be a filter in the 'cat' which is blocked, which in turn could cost me a couple of thousand pounds. (they said something along the lines of they may be able to 'burn out' the blockage (could be me not understanding though)) What do you guys think, do you think that this is the case or should they be looking for something else? If it is the cat then do I have a 'case' with lexus?, considering I use them to get the car serviced and MOT'd AND it is a low mileage car. I really have not the slightest clue when it comes to cars, answers in simple terms would be lovely, Thanks all