Car randomly won't start sometimes?

I have a ford ka that's 11years old runs perfectly when started.

At the minute it randomly doesn't want to start sometimes I manage to be it started by pressing the accelerator and only once has it refused completely. It starts but doesn't always fire straight away there's no pattern at all with it, the weather makes no odds.

But it always seem to be first thing if its not going to start it will be first time, and then its fine for the rest of the day.

Its had the spark plugs changes and leads changes from the engine (I don't know the correct name for them) and ot gets a bottle of redex every few months put through.

Apart from not wanting to start sometimes the car is fine, any ideas?

It sounds like it's cranking over but will not start from your description. Try cycling the key on (no crank) for 10 seconds and then off. Repeat this 3 times and then try starting the motor. If it starts right away you have a bad valve in the fuel pump that is supposed to keep pressure in the fuel lines. The fuel pump won't fail but you do need to cycle the key 3 times whenever you let the vehicle sit for 6 hours or more or else you'll wear the starter motor out prematurely.

Maybe the coolant temperature sensor

I'd agree with thebax2006 in that it sounds like a low fuel pressure issue at startup which could be due to a few issues like a faulty pump check valve, bad pressure regulator or even a leaky fuel injector which may cause drop in fuel pressure after sitting for a while or overnight. Has the air and fuel filter been changed? As a temporary fix, turning the ignition key on and back off a few times before starting will repressurize the fuel system for starting… If that does help, then have a shop test the fuel system for proper pressure/operation and check for leaky injectors or a bad pressure reg, etc. If a piece of debris clogs the pintle tip of an injector, it can leak down fuel pressure after sitting for a while which may cause hard starting/no start but will or may have less effect after shorter periods. A shop can also remove and fully clean the injectors with special equipment and test them for proper spray patterns… Replace any if needed. Being 11 years old, the car could be due for some maintenance in those areas of the fuel system. Would also be a good idea to have a shop clean the Idle Air Control valve (or IAC), the throttle body bore area and MAF sensor as those can get crudded up with soot/carbon over time and affect proper starting or proper engine operation.