Do all these tables reside in the same database, and does it support SQL? If so, my preference by far would be to use the SQLExecutor and do the join in the database.

Other than that I'd probably look at using a single InlineQuerier with an input port for each table.

Inside FME, Aggregator with mode “attributes only”, grouping by that attribute and set to keep all attributes.

This is also assume that the fields in those tables are unique (although you could bulkattributerename to give them all a prefix if required)

@sar_copp​ Also, you can throw all the tables into FeatureMerger, provided the Requester table is a 'parent' table that has all the ID's that would be found in the 'child' tables entering Suppliers. But I'd follow @david_r​  advice with SQLexecutor or InlineQuerier if you are familiar with SQL

I cant seem to find the correct settings as you describe above? This is an example spreadsheet where I am trying to join sheet 2 and 3 to sheet 1. All have the UPRN column in common. Is it possible? I get an error.

I cant seem to find the correct settings as you describe above? This is an example spreadsheet where I am trying to join sheet 2 and 3 to sheet 1. All have the UPRN column in common. Is it possible? I get an error.

@sar_copp​  are you able to attach a small example of the data?