Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

"There is a catch with BA, though: When redeeming your Avios for BA flights, BA usually levies large 'fuel' surcharges on award tickets plus an assortment of taxes which can run rather high.
Make sure you select the "reward flight saver" option when redeeming your Avios for that VCE flight. This will cost you 'only' 42 Euros pp on top of your Avios."

Another option -- which would cost fewer Avios -- would be HEL-TXL-VCE on Air Berlin, for which there are no surcharges when redeeming Avios. There are still taxes, however, and I'm not sure how they would compare on an AB redemption via TXL with the RFS co-pays on BA via LON.

The OP might also consider crediting her BA flights to AA rather than to BA. AA charges 10,000 miles for an Economy one-way flight within Europe (connections included), as long as the operating carrier publishes a through-fare from origin to destination. No surcharges on AA redemptions, except when one redeems on BA or IB. And only 20,000 miles one way in Economy from HEL to anywhere in the U.S. -- including Hawaii, subject to there being published through-fares -- during AA's off-peak season (October 15 to May 15) with a free stopover at the North American gateway (JFK, ORD, etc.)

Lots to consider.