You sound like I felt on completing E2E
It took me about 3 months to find any enthusiasm.The motivation to get pedalling again came from piccies & a video (by Really Ancien IIRC)on this forum of an audax in Scotland & a flickering ember,which I hope will become a conflagration, to do LEL.
I don't have the answer 'cause it's different strokes for different folks BUT
I have found that by collating a calendar of weekend rides with each ride being longer than the last & a target of a 200km ride in mid 2010 I am developing a routine & being a creatutre of habit I expect this will continue & hopefully the endorphins will return at some future time.Sooner the better obviously.
I have joined AUK to provide the routes & in the New Year will start mid-week rides of a hilly nature to improve my currently weak climbing technique.
I have also started using a fixed wheel bike to do local trips to the shops,bank or barber's.Typically a 10km journey.I do feel that this is improving my leg muscles.
After the 200km ride,base level endurance,I shall pursue an SR series & also do,midweek,short rides at higher intensity to improve speed to go with the endurance needed to do the SR series.
I have considered TT'ing but my enthusiasm/motivation does not extend to the racing-snake culture.Neither doed my XL midriff
It's a good thing that the next LEL is not untill 2013
Apologies for rambling on.I hope something amongst all that helps yourself.