It's possible that Google just feels that the text you have in your H2 is a more accurate description of your page.  Is your meta description too long?  I know that Google occasionally ignores the Title Tag and displays the H1 or other text in the SERPs if they feel it is more relevant.

If auto-tagging wasn't turned on, were the campaign URLs manually tagged?  Did they have utm parameters on them?

It is most likely a case of not having any campaign tags on the destination URLs.

I'm working on a site where dynamic URL extensions to the homepage were automatically redirecting to the regular homepage URL.  Though autotagging was turned on in Adwords, the campaign tags were being lost in the redirects meaning that the paid visits were not being tracked properly in Google Analytics.  They were being recorded as organic visits.

Double check that the destination URLs of the PPC campaigns are not redirecting, and that any autotagged URL will not redirect.

Adding the following lines to the bottom of your robots.txt should do it:

Sitemap: http://www.example.com/sitemap/uk/sitemap.xml

Sitemap: http://www.example.com/sitemap/de/sitemap.xml

If you wanted to update the file names to be different it wouldn't hurt, but I don't think you would have any problems with how they are currently set up.  If you have submitted them to WMT and they are being picked up ok I think you are fine.

Nope, but the click thru rate of the ads will affect the page's quality score and may help with future ad performance.

I've found this as a good source in the past, not sure if you have already checked it out:

http://www.internetmarketingninjas.com/blog/search-engine-optimization/301-redirects/