I've found someone who looks as if he may be a possibility.
http://www.naa.gov.au/collection/search/Harold George Jorgensen from Norway signed up in Western Australia to join the Australian army. Although he was not a British subject, he was admitted (not sure the rules here).
In July 1917 when he signed up, he was "26 years 5 months" His next of kin was mother Martine Jorgensen in Frederikstad (spelt various ways throughout the records).
In August 1919 he was discharged in London, aged "29 years 7 months"
He intended to reside at Veums gate, Frederikstad.
The timing is about right for him to work his way up from London to a more northernly port, intending to work his passage back to Norway, and then run into Blanche, eyes meet across a crowded room, etc.
I think we would need the father's name from the marriage certificate to cross-check with Norwegian records to confirm if this man is your Harold.