How can i fix my renualt card?

Ohhhhh i just dont no what to doo its driving me mad... Was on my way to work the other day when i stoped to go to shop, once backin the car i tried to turn the engine on and got "Card not detected" after about 100 atempts the engine finally started. But again every day this week iv been having teh same problem, and i just have to sit there and be patience untill my Renualt 54 plate, decides it wants to turn the F*** on... i dont have a spare key and im worried if this one completey cuts out and goes... Ive read that ppl have took theres to a shop in london but im from derby :( any more ideas??
Kirsty