Vauxhall Corsa automatic gearbox "range switch" problem?

My daughter's car an automatic gearbox Corsa has developed a fault whereby it appears to lose power intermittantly when accelarating away at traffic lights. We appear to be able to get round it by changing gear manually and have been told that it is the "Range switch" in the gearbox causing the trouble. Being a student, she is concerned that the estimate for the part alone is £200, is this correct, or are their alternative ways of solving the problem.?