Potterhead7

My boyfriend's 2004 Citroen C2 has a problem which the Citroen garage can't diagnose. The power steering and speedo randomly cut out for a while and then come back again while driving. The garage say they can only diagnose while its happening but it is literally impossible for my boyfriend or anyone to get the car to the garage at the drop of a hat! Last time we tried it had come back by the time we got there. I'm so worried he will have an accident, the roads he drives every day are so bendy. Does any one have any ideas? It has happened three or four times in the last three months.