Well Malcom - just where to start.
Might simply try to work in the order you have made your enquiry so it should flow better.
Firstly - I suggest you ignore the Rootsweb reference as far as this discussion is concerned.
Rootsweb, like IGI can be very misleading at times. (I was only looking for something in IGI last night that shows this - I have reference of a Will for one Daniel Davies who died about 1776. He left his bequests to wife Catherine and daughter Elizabeth (now Jennings). I have now found that Daniel DAVIS married Catherine STEVENS in 1770 or 1771 and that Elizabeth was from his first marriage in 1751. IGI shows Daniel DAVIS born 'abt.' 1756 so someone is completely lost!)
Now, before I tell you what I know of William POLLARD.
Were there TWO marriages of a John POLLARD to a Margaret BECKERLEG
- My records show that John POLLARD married Margaret BECKERLEG 7th May 1785 at Paul.
This John was the son of the subject of your enquiry.
William POLLARD was baptised at Madron 30th January 1730 s/o John POLLARD and Ann (nee RODDA).
John was baptised at Morvah 10th August 1684 s/o John and his (currently) unknown wife and had siblings Florence, William, John and Jacob that I am aware of.
From the information I have William was the youngest of eight children all of whom were baptised at Madron except Phillis who was baptised at Paul in 1721.
Elizabeth HEAD was baptised 1st January 1732 at Paul (Jelbart Society/IGI) d/o John HEAD and Constance (nee GILBERT).
AHA! - now I see the problem with John POLLARD/MargaretBECKERLEG - you seem (I think) to have given the incorrect date.
Barzillai BECKERLEG married Margaret HEAD 19th October 1749 at Paul.
Margaret was the daughter of John HEAD from his FIRST marriage to Margaret GWAVAS.
John and Margaret were married 23rd April 1726 at Sennen and Margaret was buried there 3rd April 1727.
Margaret HEAD baptised 8th March 1725 at Sennen (born 28th February 1696 d/o Robert GWAVAS and Rachel (nee REED).
Robert GWAVAS married Rachel REED, of Sennen, 3rd November 1694 at Paul.
Rachel was the daughter of Tobias REED.
As for the adult baptism - this is something I have seen several times and usually seems to coincide with an impending marriage although I cannot say that I am sure of the reason.
Perhaps more interesting is that two known sisters of Margaret (Jane and Rachel) were baptised at Sennen 22nd March 1717.
Jane was born 9th February 1698.
Rachel was born 28th June 1701.
Now I wonder if this has anything to do with the Quakers.
I would suggest the high likelihood that Rachel Reed's father, Tobias, was the son of George and Ann READ - this was one of the Quaker families of whom you will find information in West Penwith Resources and was discussed in another thread a couple of months ago.
1658: Tobias Read of Sennen son of George & Ann Read to Margaret Thomas
of Market Jew (Marazion) dau of John & Francis Thomas.
The eldest of three daughters I have for Robert and Rachel GWAVAS was named Margaret and I suspect she was named for Rachel's mother.
The next daughter was Jane and she would have been named for Robert's mother.
So were these adult baptisms actually 'second' baptisms because the girls had originally been baptised as Quakers and were not recognised by the Established Church.
Refer to yesterday's discussions re the variations of the name - but I would say that these are all GWAVAS variations.
I have not done much work on the GWAVAS family but I note there are only 74 events for them recorded in IGI.
The bulk of these events are at Penzance and then Paul but there were several entries for Sithney also.
Finally - I should tell you what I know of Constance GILBERT, second wife of John HEAD.
She was baptised 6th March 1697 at Morvah d/o William GILBERT and Elizabeth (nee DAVYE).
William was baptised at Morvah 12th August 1666 s/o William GILBERT and Margaret (nee PENBERTHY).
William was baptised at Morvah 24th September 1630 s/o Thomas and Blanch.
Some of this information was from the Jelbert Society and other from my cousin Nancy in Truro (interested in Pollard and Jeffery amongst others).
The remainder I have worked on myself as further resources/information became available and I am 'reasonably confident' of the whole scenario.