email's fine... Myrna & I communicated this way - for almost a whole year in fact - and it ended up looking almost like a book! But that was just US! Indeed when it came to submitting Xerox copies, we wondered if the ECO would even bother going through it all with a fine toothcomb.
And besides, the British Embassy staff are well-aware of the problems involved in relying on handwritten letters sent by "Snail Mail".
Keeping a daily log, or diary - as Joe suggests is a good idea too.