Well if I interpret the information correctly, then if for example your cables going across the joint/connector was red, white & blue - then you would cut out the connector and join the red cable back to the red cable, the white cable back to the white cable etc. This joint would need to be either soldered and then wrapped in tape (I personally would use heatshrink tubing) or connect them using through crimps!
This may well be the problem or you may still have to try a fault code reader with a fault code reset button (i.e. it will extinguish the fault that was bringing on the light) I have one which I bought from Argos which I use from time to time and it works very well:
http://www.argos.co.uk/static/Product/partNumber/7402742/Trail/searchtext>FAULT.htm
Note: This device will only work on petrol cars from 2001 and diesels from 2004 onwards.
It costs £20 more now than when I bought mine a few years ago but it represents good value for money to me. There is a more expensive version available but I think you will be fine with this one! If this all fails then you may have to bite the bullet and visit the main dealer, but as suggested a good independent Peugeot garage might be best to make your pound notes go further.
Good luck