First depends if the garage plugged it into a puter, my mum's corsa did that twice, complete loss of power jumping all over he road, turned out the fuel to air mixture sensor wasnt working.
second thing is the fuel pipes, try putting a filter on the pipe that comes from the fuel tank or before it gets to the engie, just run it for 10 mins, or even do a small circuit in it and check the filter for any crap, if it gets blocked quite badly then yeah you might as well get rid of it because a majority of that crap will be lying in the engine, unless you fancy stripping it down. If there is no crap in the filter then i'm not sure what else it could be.