Stefan - I believe that the best ( perhaps the only ) source in the UK will be Dave Jarman at DJ Road & Race Services - see the top of this Website for his details.
Group 5 big wings front and rear, front spoiler, nose cone
rear 3 piece spoiler
tailgates
bonnet
all available in materials of your choice and budget
all lightwieght racecar application or can be made up for road use.