megane wont start?

2 choices phil, disconnect the imobiliser, or buy a complete new lock set and keys, this will replace your old ones, But, will not be cheap, could be looking at £40 upwards, then the labour, which will cost as the barrels have to be changed, and that is an extra charge, !! depending on your immobiliser it could possibly be just a loose wire, if connected to the battery, dont go to renault as they will rip you off, try the motor factors for prices, and a little local garage.
hope this helps...

chell'e
January 2009