reason it wont start straight away is prob to do with coolant temp sensor reading the wrong temp !
code p0118 change the coolant temp sensor , rubber o ring and clip (around £28 from dealer)
code p0420 is the cat converter , is it standard or decatted ? if standard you need a new cat
code p0341 has it had a cambelt change recent ?
i would start by changing the temp sensor first as this will make the car start and run correctly and then clear all codes as it could well be the cause of the p0420 cat code cos the fuelling is incorrect , and go from there