I tested 90% British Isles/10% Persian/Turkish/Caucasus. My family has 100% German surnames from German-speaking countries. I was upset enough when I got my results to take a test from another company, briefly wondering if I was adopted. I got some comfort from my second test which showed a more diverse Northern European background. Take note of the fact that Ancestry DNA is still considered in "Beta" and I'm hoping/expecting that the percentages will be adjusted at some future date.
When you have access to the raw data (another "promise" from Ancestry), it may be enlightening for you to run the admixture tools available for free online. You may find that your results are more in keeping with your known ancestry. I have read that many Ancestry customers are dissatisfied with results in the British, Scandinavian, and German areas - not sure about others.
I'm curious if you've found any actual matches with your Ancestry results. That's my other concern. So far I have over 1500 "matches" here with zero results. I have had better, still minimal, results elsewhere. Still hopeful for the future. So many people are testing it should help not only your matches but the ethnic percentages too.