Sorry, just updating for benefit of others:
Sent off my form on 5 October, of course ticking the box that I am subject to immigrant control.
Decided not to wait the 4 weeks it tells you to before calling, so I call after 3 weeks on 27 October. The person on the phone was very nice and looks up my application. She says it was received but the paperwork hasn't been sent out, so she marked my case to send the paperwork out that day.
Yesterday, on 6 November I receive the paperwork (I've thrown away the envelope, so didn't see if the postmark really was 27/28 Oct or slightly later, but with all the postal strikes I wouldn't be surprised it took 10ish days to reach me). It's 1 sheet of A4 with 9 questions...but only the first 3 apply to me since my husband is British (I think the rest deal with right to abode & EEA stuff)! Seemed entirely pointless and something that could've easily been done over the phone, as all I had to put was that I was subject to immigration control, my nationality (USA) & his nationality (UK). Then a signature and back into the post! I suppose they decided they need a written record & signature just to cover themselves and have official record, as I know people a few months back did all this over the phone.
I'll update again when the money is in my account, but I'm going to give it around 10 days and phone again to make sure they received it as I don't trust the post lately. A normal app takes around 10 days to receive the money, so this feels long enough to me.
Phew!