Hi Alastair,
I agree with your lineage back to John QUIGGIN/Mararet Cain. Another possibility for John's parents is another Jon QUIGGIN/Margaret Caine.
"IGI Record Jon QUIGGIN

Christening: 25 Jan 1710 Kirk Michael, Isle Of Man, England

Parents: Jon QUIGGIN Margt CAINE

Batch number: C048991 Source Call No. 0106737

Printout Call No. 6909423 Dates 1611-1849"
"IGI Record Jon. QUIGGIN Margt. CAINE

Marriage: 31 Aug 1708 Kirk Michael, Isle Of Man, England

Batch number: M048991 Source Call No. 0106737

Printout Call No. 6909424 Dates -1629"
his parents could be:
William QUIGGIN of Shylchaag Abt.1676-bur.01 Mar 1738 and his second wife Margaret Taylor/Tailer (first wife Margaret Moore QUIGGIN - Margt ALS MOOR 28 MAR 1732 KM burial)
his parents were:
Jon QUIGGIN c.28 Feb 1640 KM-bur.30 Jun 1727 KM and Ellinor McBooy c.08 Jun 1645 KM - 23 Feb 1723 KM.
her father was Phinlo McBOOY.
"IGI Record Ellenr MC BOOY

Christening: 8 Jun 1645 Kirk Michael, Isle Of Man, England

Father: Phinlo MC BOOY

Batch number: C048991 Printout Call No. 6909423

Source Call No. 0106737 Dates 1611-1849

Source Call No. 0106178 Dates 1849-1883"