Panasonic 100-300 or Olympus 75-300 (m4/3) Please Help!!!

with a name like "bangers & mash" I'm guessing you may be UK based, if so you can still get the 75-300 new from here http://www.srsmicrosystems.co.uk/5753/Olympus-M-Zuiko-Digital-ED-75-300mm-F4-8-6-7-MSC---Black.html  (reduced in price)

I got mine used from one of my preferred dealers for less than the panny 100-300 (with 6 months warranty) and its been a relaible and useful lens for birding and nature work

I don't honestly think there is a lot of difference between either option, I happen to like the extra 25mm at the wide end with the 75-300 but doubt I would have got it at full price