"St. Patrick being an Englishman?"
For the record, St. Patrick was born in Kilpatrick, near Dumbarton, in SCOTLAND.
Unlikely and debatable. If you know your history, Scotland did not exist at the time of St Patricks birth - it was known as Caledonia by the Romans and inhabited by the Picts. The Irish Scots tribe did not invade from Ireland and give their name to this region until the 6th century. Thus, even if St Patrick was born in Kilpatrick, which many doubt, it was not Scottish at the time, therefore he was not Scottish. Caledonia was not colonised by the Romans yet St Patricks name, Patricius is clearly of Roman-British descent, something which would be very unlikely in Celtish caledonia at the time.
So, we can conclude that he defintely wasn't Irish, definitely wasn't Scottish, but that he was probably of Romano-British stock and given his name, he was likely to be from below Hadrians wall rather than above it.
St Patrick was born in Bannaven(m) Tabernae. Nobody really knows where that was born, but the more likely ones are in Wales or my particular favourite since I used to live near it, Bannaventa in Northamptonshire which is not only on the main North-South road, but its name is simply a contraction of the stated birthplace (in the same way Lincoln is a contraction of Lindum Colonia). Scotland seems unlikely because being north of the wall would mean it would be at best an outpost, not a place where "Thousands" of people might be captured.