Hello MrJamesgroves........
I do Jersey quite often and I can't think of any reason to go via France. I fly form White Waltham in a P28A and it normally takes around 1hr 45mins brakes off to brakes on. I route SAM DCT ORTAC and Solent approach are usually very helpful. HOWEVER, there are a few NOTAMS out for this area at the moment so make sure you check them before you start your flight planning. You will need to file a GENDEC 12 hours before you fly as The Channel Islands still fall under the prevention of terrorism act, also you need to file a flight plan at least 1 hour before you take off, on the flight plan they like an EET for 50 north.
Landing charges are very reasonable in Jersey, if you are under 1000Kg then it is £8 + £5 admin........this also includes 7 nights parking !!
You can also claim fuel drawback which works out at around £54 on our Cherokee.
Send me a PM if you would like me to send you GENDEC, Flight Plan and drawback forms so that you can complete them on your computer and keep them for future reference and use.
Hope you have a good trip,
Regards
FBW