2004 Renault Megane can't start car

Partner drove through deep puddle 6 days ago got to house , after car was parked up it would start as normal but all my electrics were on ,wipers,door lights all lite up, lights and indicators all on ,and engine light was on and so was electical fault showing on display, the car couldn't be driven as steering lock was on and the only way to stop car was to stall it ,so I get a garage to come and collect a d fix it and next day get call it is ready ! The car does not start a d garage owner phones the person who was dealing with it to get it started after a while he turns up and after revving the guts out of it it starts so I go to work and after work it doesn't start at first it was trying but after 10 mins of waiting all it does is say service in red light of immobilized is on full and two bleeps sound ? The mechanic said that my fusebox was full of water and he drained an cleaned and protected it but he added he couldn't get into my immobilser as no wheel locks were left even though I showed him in the glove box ?
Sorry about the story anyway the car I can get into and lock and unlock but won't go + wene I do try it after I am inside I have to press the start/ stop button to be able to use key or it won't lock for me ?
Can you help or suggest a temp sollution to get me to a garage ?