and another update - issue finally resolved!

after endless discussions (or rather being on hold) with EXPEDIA I managed to have a word with their floor manager (in the call centre) who was, not surprisingly, more helpful than all previous expedia employees. Last night he assured me that despite initial refusal by KLM to authorize change they DID eventually receive authorization and change is in process. I was checking my itinerary today all morning and hey presto, name is updated.

In the end I didn't even need to provide them my marriage certificate despite my offer to fax it.

So advice for everyone, make sure you book in a right name but if you don't, it IS POSSIBLE to change it if you're persistent enough.
Thanks to all who participated in this discussion!