lookup and list matches of a ref no with multiple occurrences

[SKooLZ]

Hi excel Gurus...

I'm back for your most valued assistance with a formula.

I have uploaded a sample file. Sheet 1 is the master list
W1, W2,W3 and different sheets in the workbook named after their Ref no.s in cell A1

I need formula in each sheet to lookup the cell value in A1 against the master list (Sheet 1) and list the values of column B in the master list where a column A matches are found but not duplicate the Column B entries. I have started an INDEX match function however it's duplicating the column B results.

PLease Please Help!

Many thanks in Advance!