FLRM wait times (by post)?

Just wondered what people's experience has been with applying for FLRM extension of stay as a spouse? I am hoping to do it by post to save the extra £200 for priority service, but my husband and I are reluctant to hand over our passports for up to six months.

Also, how much time does it take when you go for the biometric testing? I will have to travel from Lincoln to one of the centres, probably Croydon or Sheffield.

And is it really true that if you apply with your marriage certificate, you don't need to supply six documents (bills etc) documenting your relationship? It seems to only be mandatory for unmarried partners, but this seems to good to be true.