I thought I wasn't sure about the fire engine, but it does have the same wheels as my Bruder wheeled excavator. I rather like Bruder vehicles, and have a collection of their construction vehicles but they take up even more room then Playmobil does! 
The ambulance in your top pic looks strange, Gordon. It looks as if the 'ambulance' logo has been added afterwards (photoshoped you could say) because it doesn't look level and in line with the rest of the vehicle 
The fire engine is certainly built around Bruder parts, not only the wheels but the ladder, too, and the front and some small parts.
Jo Litchfield is a prolific modelmaker and book illustrator and her books have been translated in foreign languages.
Here's another familiar shape:
http://www.bargainbooks4kids.com/images/trucks.jpgMaybe no credits are given to Playmobil because while Bruder provides the trucks etc free Playmobil has to be bought in the local toyshop.
I think you're right about the ambulance, Damo; I hadn't noticed that before.