renault megane 2003 authenique?

My friend recently bought a Renault Megane, and almost immediately the air-bag light and the service light on the dashboard stayed on, the left hand indicators were playing up and the left hand side light did not work. She took it back to the dealer, and after several attempts, they sorted it. However after about a week, the engine and lights would not switch off, so we disconnected the battery, but when we reconnected it all the lights came back on and the indicator lights stayed on constant. She contacted the RAC and they towed her home, however, the battery is now flat and we cannot get into the car to release the bonnet to jump start the battery. Could you please advise as to whether the problem is the solenoid, and how we can gain access to the interior to release the bonnet. We have tried the key, but it doesn't seem to work.