Accept the fact that in Germany the aerospace vertical is a closed "old boys" club.

So you need to consider 3 approaches:
1) Since you have some contacts already, you need to nurture them and expand your network by asking for introductions. Do not pitch them, just let them know what you are doing and ask for help.
2) Find a way to scan/review all the listings in Germany for companies that have just been incorporated and select the companies that fall into your area of interest, Approach these companies with a personal letter to the founder. This can be expanded to all Europe/UK.
3) Get LinkedIn Sales Navigator and screen for companies and people of interest. Again, please do not pitch right away, instead focus on building relationships.