All the relevant answers you are likely to find were in those links. To summarise:
F1= no flame detected
* No gas or faulty gas valve
* Check flame electrode and cable for defects
* Check ign unit on gas valve
* Check fan operation
* If boiler has overheated reset the overheat sensors located on the left hand side pipework - little red switches on a sensor attached to the pipe.
* CVI unit could be faulty
* Possibly air pressure switch
I believe jaguar boilers were made by Glowworm. I also believe that Glowworm offer fixed price fixit. I have used them myself on two occasions. the advantage of getting the maker to do the job is the engineer will have specific product knowledge and will have a van full of product speciific spares - they are also reasonable price.
Oh, they are also Gas Safe certified so can work legally on gas installations, whereas those who are not certified cannot legally do so.