Anti Pollution fault - Peugeot 307 1.9 hdi?

Ive had my 307 since January this year, its 51 plate had no problems however about 2 months ago the Anti Pollution fault came on. The fault cleared when the engine was restarted or after putting diesal in. Drove the car this morning for the first time in 3 days and the anti pollution fault came on 11 times during what should have been a 20 minute journey. Each time the power went had to pull over and restart the car. Spoken to a garage who advised that it needs some sort or serum and it will cost £200. Does this sound right?