hi kimmi
yes you can use some of the old sponsors documents like payslips/mortgage statements but 100% you MUST supply 6 months up to date documents prior to the date of application.

and ok not to supply consent letter. some documents on the above list are not a requirements.

cynthia never wrote application letter, just a filled in VAF2

we printed most of our emails, 26 A4 sheets of paper

captured screen shots of yahoo messenger archive around every week or so (we chat nearly everyday) and printed these, they did not contain much of the conversation only a few of the opening lines and showed the dates above that we have chatted.
EXAMPLE

(i kept a 3rd copy of documents here in the united kingdom, just in case a document went missing. brings back good memories just looking at them, basically tells the story of your relationship, how it developed over time.)

hope this helps you
martin