Just to add- not a boast....
when my wife 1st came to UK on 2yr spouse visa from russia, i planned a surprise trip to Paris. didn`t even research about Schengen and only heard from a mate at work about it! By this time there was no time for visa app and just chanced it on the friday evening.
french ferry port workers were on strike and ferries were getting cancelled etc (heard on radio on way to Dover!) pressed on and presented my UK passport and her Russian (with UK spouse visa) to customs lady @ Dover. with t5ickets etc (P& O) ....as we were checking in (with NO probs) our ferry was cancelled and were offered to change to seafrance said, yes.... drove out of port and back into arrivals (seafrance) through UK customs. Queued at departures/customs handed over docs NO problems again onto ferry, off at calais, and off to Paris collecting lots of Brownie points from the wife on route!!
The only thing i can think is that BOTH customs people didn`t know requirements or didn`t care as the french would get us on the other side OR because i was in uniform (British soldier- just finished duty before mad dash to port....)
make of that what you will- it ain`t over til the fat lady sings... or says NO!!!!