5 month tour - spares/ tips?

Hi all, after much planning we are heading from Scotland to Europe shortly. We are travelling Newcastle to Amsterdam, down the Rhine valley, to Tuscany, Croatia, the alps for a month, then on to Hungary, Czech Republic, Romania, Poland, Lithuania, estonia, Latvia, Tallinn to Stockholm ferry, Sweden, Norway, Kristiansand to Hirtshalls ferry, Denmark, Germany then home. 

All ferries and most sites that we can book are booked. 

The question is - what will break/ what spares needed? (We have all the essential vehicle safety kit, including wheel chocks required in Latvia...)

Any experience/ tips? 

Jim