Aegean Airlines are now advertising flights from Heathrow through to Lesvos (via Athens) for spring 2011 - good flight times in both directions and good prices at present.
Olympic Air have yet to advertise their Athens to Mytilini flights, but Heathrow to Athens flights are available.
Athens can also be reached by British Airways (Heathrow) and EasyJet (Gatwick and Manchester).
For more info see the Lesvos Birding website.
Thomsonfly are advertising charter flights from 14 April 2011. This year the 15 April flight was cancelled and the first flight that flew was on 22 April. So anyone traveling before 21 April might want to think twice before committing to charter and go via Athens instead.
I'll post any news I get on all flights on my website as and when and link from this thread. Please feel free to contribute anything you find yourself.
I have again arranged a discount for birders with Tsalis car hire. See the Lesvos Birding website for further details.