awk  ' 
BEGIN           {FS = OFS = ";"
                 print "ean;sku;pps_reference;mpn;stock;price;manufacturer"
                }
FNR  == 1       {FCNT++
                }
FCNT == 1       {for (n = split($1, T, ","); n > 0; n--)         MFC[T[n]] = $0
                }

                {gsub (/ /, "", $1)
                }
FCNT == 2       {for (n = split($1, T, ","); n > 0; n--)        {SKU[T[n]] = $2
                                                                 SUP[T[n]] = $3
                                                                }
                 next
                }
                {for (n = split($1, T, ","); n > 0; n--) if (T[n] in SKU)       {$2 = SKU[T[n]] OFS $2
                                                                                 if (MFC[$NF] ~ SUP[T[n]]) print
                                                                                 else                      print $0, SUP[T[n]] > ERRFILE
                                                                                 next
                                                                                }
                }
' ERRFILE="wrong_match.csv" manufacturer_compare.csv website_clean.csv supplier_clean.csv
ean;sku;pps_reference;mpn;stock;price;manufacturer
4260010852693;P00002801;1043154;84;743.42;70100118555;Fujifilm
4960999575285;P00002800;273189;9400;141.80;2768B016;Canon
0088698115763,3141725001174;P00002631;3654125;20;54.80;C1825A;Hewlett Packard

cat wrong_match.csv 
4000461034213,4960999575292;P00002799;27433196;44;44.94;2768B017;Canon;Dörr