Well the above code didn't work but I managed to solve it. Thanks Dip11, without your input I wouldnt have completed this. I thought someone might find this useful in the future so posting the completed formulas.
I am just using an "is in stock" function in my backend so dont need quantity, just 1 or 0. I set the "is in stock" to <=1 because I like to be ahead of the suppliers 
New price and stock list where:
column A is sku
column B is price
Column C is stock qty
Catalog needing updating where:
Column D is sku
Column E is price
The formulas will search through the old catalog and new pricelist irrespective of sku order and if a price or stock has changed will adjust it.
It will remove sku's that dont appear in the new pricelist and add new ones that do with their price and stock.
sku column
price column (with markup and vat added if you need it)
stock column
If you want a bit of detail then the following might be useful too.
end of life items no longer in pricelist:
~W
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