Emissions Light on sporadically and cuts engine

Hello, I have a 2002 Renault Clio with the 1.2 16 valve D4F engine. The emissions light came on whilst driving on the Motorway (75MPH) and completely cut the engine power. I stopped for a while and when I started the car again the light had gone off and drove fine. I took it to a garage who plugged it into a diagnostic and lambda sensor after cat and coil pack fault codes came up. I had the codes cleared and replaced both components however the light keeps coming on. It will happen at various speeds and sometimes it is possible to 'bump start' the car by putting the clutch in and releasing it when the engine has cut out so that it starts itself again. My fuel economy has been REALLY good recently and so I think the problem is causing the engine to run weak. I am going to have another diagnostic test tomorrow but I need the car running again ASAP. I was thinking the fault could be the other lambda sensor needs replacing or the MAP sensor or Throttle Body? I can't afford to keep replacing things until the problem goes away. I really don't want to give up on my car but I need to get to the bottom of the problem soon as I am losing faith in it. Has anyone had this problem before or does anyone have any idea on what it could be? Thanks in advance!