Well, I said I'd update this thread once my 23andMe results arrived. Unfortunately, I'm as confused as ever!

Here's my 23andMe Ancestry Composition (Standard Estimate, Sub-regional Resolution) Northern European results:

Northern European
9.0% French & German
1.3% British & Irish
0.3% Finnish
61.5% Nonspecific Northern European


When I change the composition estimate setting to Speculative, here's what my Northern European results look like:

Northern European
31.7% French & German
16.4% British & Irish
4.1% Scandinavian
0.4% Finnish
31.6% Nonspecific Northern European

I am no closer to figuring out my paternal grandmother's roots than I was before...I wish I could confirm that the British/Irish DNA existed, as this would be a HUGE clue, but I cannot at this time. Very interesting nevertheless.