Fan will not come in on my 2005 ford focus and i have fitted a new sensor to the back of the engine

did you use a universal )2 or a direct fit? the universal will not work properly on a fordfocus.
also double check that you didn't put the wire too close to the exhaust and make sure the wire is plugged in tight

Hi,i had similar problem,the fan wasn't working.When i turned heater on hot it released the heat from the engine & temperature went back down.Turned out my fan relay fuse had blown.$5 fixed the problem.Hope this helps.

follow the wires back from the sensors and you will find that they go into one connector for the reversing lights,just disconnect(or fit an inline switch) to disable........(why?).

Yes you can manually operate the fan with a switch, but if you leave it on all the time, you will waste enough in gas to pay for a new relay.
If you forget to turn it on when stopped in hot weather, you will blow a head gasket.
A new relay is only $15, so why not just go to Autozone and buy it?
But also check the radiator temp sensor first, by seeing if the fan comes on when you shunt the sensor?
If so, then it is the sensor, not the relay.

Loosen the adjustment bolt on the alternator, remove old belt, fit new one and stretch it slightly with the adjustment of the alternator until you have 2mm of deflection. Tighten up the bolt and take her for a run to charge the battery properly.

Maybe a stray leaf, twig or other small object has been sucked into the ventilation duct, touching the centrifugal fan.
You need to pull off ducts around fan and inspect.

One of the air intake pipes had come loose. Fastened the jubilee clip back up and it was like having a new car!

With the sensor unplugged and the fan works,, replace the new sensor,,,,, it is probably defective. I have seeh this before.

if the numbers on the bottom of pan match .

You would really need it to act up at the garage, then they should look for crank signal, I have seen the wires backed out of the connectors on the crank sensor.