Advice for any road trip:
- Know the local rules and regs, quite a few countries require a hi-vis for every seat as well as a set of spare lamps, warning triangle, ect. Depending on where you go there may also be a requirement to buy a Vignette or local emission / congestion charge,
- European breakdown cover is a must, saved me when I had a coil pack fail on my LCR in the middle of Germany,
- Always carry your V5 and a print out of your insurance documents, keep scanned copies (Drivers license and Passport included) on a dropbox as well in case any were to go missing...
- Learn the local language, obviously don't expect you to become fluent overnight but simple phrases and sentences and attempting goes a long way,
- Modifications: As usual, you're expected to declare any modifications to your insurance company and ensure it's road legal. German and Austrian Polizei are very good at catching people out on this. They have (like any police in the EU) the ability to make your car Verboten for the public highway, which means it can only return to the UK, on the back of a truck... very dull.
Boring stuff aside, If Germany and Autobahn is your thing, you can do a tour of the big German Car makers. Wolfsberg (Highly recommended), Stuttgart, Munich, and Ingolstadt.
Further afield you have an abundance of mountain passes between Switzerland and Italy but do check when they are open due to skiing seasons.