Are the LEDs in parallel or serial? If serial you can calculate the total voltage of the 40LEDs and use a step down transformer. Otherwise if it is in parallel, I think you will have to get about 1-3V from a 230V supply. In that case find a 230V to 12V stepdown trasnformer. then have to rectify it to 12V DC. Then send that rectified output to a Voltage regulator like the LM78xx series. then only you could connect that out put to the parallel led set.
Note: I am not sure at what voltage the LED will work. So you better ask it from someone at an electronic shop. Also depending on that LED voltage only you will have to select the voltage regulator model. For eg if it is 5V you could use the LM7805 model. Best thing is to go to an electronic parts shop and tell the guy your requirement and he will help you to find the correct step down transformer,rectifier and voltage regulator.