peugeot 307 hdi keeps cutting out?

my car has been in the garage now for 3 weeks cant find whats wrong with it ur just driving along then anti pollution fault comes on and car just cuts out but if i leave it for about 20-30 mins it starts up and drives again but only for so long then same thing happens again garage has had it on comp no faults had lecky guy looking no faults so he put new fuel pump in 256pd got car back on tues was out yest car broke down again!!!!! back to square 1 but 256pd out of pocket anyone any ideas???? getting really stressed and am 4 month preg not good for me or baby :-( had car 7 year and this the 1st problem ive had apart from replacing adative tank 3 year ago which cost me 600pd