Hi Thomas, I do not have a list the names of the vessels convoyed in the French Coal Trade, but as a start I can give you a list of vessels sunk carrying coal from the UK to France during March 1917, whether they were in convoy or not I do not known.
CHATHBURN 1942grt 1st March
MUNIFICENT 3270grt Ist March
CHARLES LE COUR 2352grt 11TH March
AMBIENT 1517grt 12th March
GIRDA 1824grt 13th March
HAZELPARK 1964grt 20th March
BYWELL 1522grt 29th March
All the above taken from Lloyds War Losses.
Regards