I thought it interesting that having got his grandmother's marriage cert, which showed she'd married in a register office, they just automatically decided to check synagogues. My first thought - and I would guess, most other peoples - would have been to see if there were any children of the marriage. The fact that they just jumped to a syngagogue didn't ring true, and how did they know which one to choose? I suppose they had to get the link to the synagogue and granny becoming Jewish somehow.
I liked the way the American guy showed his research. Looked for a death of granny, couldn't find one so looked for the death of her husband. Found it, got the certificate and then found granny used a different Christian name, so checked for deaths under that name, then as she was only about 60 when her husband died, looked for marriages. At least it showed how to get round difficulties in finding people in records.
Lizzie