Not sure if the more modern cars have metric fasteners (my car is mostly imperial but I have used metric stainless in lots of unstressed areas) ..... I have some great spanners with 10mm one end and 13mm the other two most used sizes (I also have 17mm one end with 19mm the other)... saves carrying two of each .... if you can't find them elsewhere lots of cars had them as part of the vestigial toolkit in the spare wheel so there's plenty for the taking in any scrapyard.
K Lots on ebay 
"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10
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