I know this is old but most Google searches don't tell you exactly what to do and if you are new to Chrome and hate British jargon here is how to get RID of Under the Bonnet: make sure you go to: chrome://settings/advanced
Select the WEB CONTENT section and then click on the Languages and Spell Check settings button (or use language link as cave_troll said).
If you only have English (United Kingdom) you can add English (US) using the ADD button at the bottom.
If you have more than one English selection highlight the one you want and choose DISPLAY GOOGLE CHROME IN THIS LANGUAGE button (it should appear to the right of the language selection box).
Then close all your Chrome windows and re-open them.
Voila.. Under the bonnet gone (or whatever other language idiosyncrasy was in there).
Now you can go back to chrome://settings/languages and simply highlight the language you don't want there and click the small 'X' at the end of the highlighted box to get rid of it and it won't come back. Alternately you can leave the languages there and just shuffle them around by click and drag so its available for a quick change.