Ganspette to Ans du brick

Hi there I'm taking our 1st trip abroad to these 2 places next month & hope were ready (got all the docs, breathalyser etc...) but was wondering about 2 things. How long in the real world would this take to drive (Gandspette to Ans) via the motorways. Sat nav recons 5 hours (but that's  non stop) And the second thing is Sanef or similar. Is it worth in in August? I do have to go back to Gandspette for 1 night before going back via Calais.

Any advice would be greatly received