PING!, Email from SAS thougt I would share. Also look at this flight comparison though as easyJet is also doing Helsinki flights but from Gatwick. Helsinki is in the Euro zone and wasn't cheap to start with so I'm not suprised there is a flight sale on!
"SAS/Blue1 have just reduced their price from London Heathrow to Helsinki; you can now save 15% on flights*. London Heathrow - Helsinki before £69 - NOW £59 one-way! Hurry, sale ends on Monday! Book Now.
Not only that, but you can get a 2 for 1 Audio City Tour (worth £22) to explore the capital. Read more. And remember, kids get 25% discount.
* Fares incl. taxes and charges. Subject to availability. Terms and conditions apply. Travel period: 1 August – 30 September 2009."