There is no need for Customs Clearance ex UK for a flight to France. You may file an online GAR (General Aviation Report form) if you wish but it is not mandatory for an outbound flight to the EU. The GAR or inbound customs clearance is of course required for the return to the UK.
If what you are thinking of is a refuelling stop, then Southend is probably not a good idea for the next three months due to work in progress on the airfield and a requirement for mandatory handling.
Last edited by Tagron; 10th Mar 2017 at 16:18.
Reason: Addition