Hey Griff, welcome! I have a really cheap OBDII bluetooth dongle and the Torque app on my Android. It works well and reads most (but not all) sensors. A separate plugin for Torque can be purchased for under a tenner which claims to read the additional Renault codes but I've not bothered with this.
Maybe check your sensor and reduce the BAUD rate as low as possible? Also check to see if it can be set for maximum compatibility?
When you say you're fixing it up what are the problems buddy? It's a refreshingly simple car and you'll get loads of help on here, on the Facebook RS133 and Facebook Twingo Owners forums.
Welcome to the gang!