I am new to this forum, but thought I would post my own data point.
15 Sep: posted SET(M) application
16 Sep: credit card charged, acknowledgment mailed
24 Sep: I got invited to speak at a conference on 7 Nov
early Oct: My husband got asked to undertake work travel
mid Oct: I found this forum and discovered to my horror that the "aim to process 70% of apps within 4 weeks" did not reflect reality for either FLR or ILR
23 Oct: My husband sends a letter to the Home Office, as advised by general enquiries line, with letters of support from his employer & my conference, asking very politely if anything can be done to expedite matters. Nothing is heard until...
5 Nov: Eight hours after I've concluded that I will miss the conference, the Special Delivery registers as on its way
And of course the Special Delivery was late, which caused its own set of problems. I ended up travelling on a second passport I'd acquired from the US embassy (on the same basis of urgent unexpected travel) but waiting to hear from my husband that the visa was really there before getting on the plane.
So that's 7.5 weeks for me, with a "pretty please" letter that must have worked.