Find and match partial text between 2 tables, return value

[BudgetGirl]

I have a budget workbook which, along with other information, I import data from various financial institutions every month containing "Transaction Details" which I need to categorise and allocate. The data is never in a consistent format and the information I need to categorise against the budget can be contained anywhere in the "Transaction Details" text. Once categorised, I have various formulas and look ups that updates the rest of the sheets.

I have tried to automate the categorisation process but it never seems to work how I want it to. I set up 3 worksheets, "BUDGET" which is the main sheet and has the control Categories. Then I have the "DATA" sheet which is where the imported data goes, and contains an additional field for "Category".
Then I have a worksheet (WS3) that I put "common entities" in Column A and the related BUDGET category in Column B (which links to the BUDGET worksheet, as some categories have data from many like entries (eg. "Groceries" could be from Costco, Aldi, Farmers, etc).

I want to be able to look for partial text in "Transaction Details" on the Data sheet against column A in WS3, and return the result in Column B, eg. ='WS3'!B5. Then if we decide to change the category linked to a supplier, I can change it in the WS worksheet.I have tried various LOOKUPS, MATCH, but can't seem to get it to work.

Sorry I can only supply images as I can't download software on corporate machines.
Thanking replies in advanced