Can't find corrext Index Match formula where different options have same sub-options

As shown on the attached, pricing list has four criteria, three (Supplier, Product Types and Finishes) are in columns, and the Size is in rows.

Challenge is that each Product Type has the same two choices for Finish.

Currently calculating the correct price by "nesting ifs" matching every permutation of Supplier, Type, Finish and Size to each column of prices.

I know this can be done by one overall Index/Match, but just can't work out the correct structure!

Hope someone can see the wood for the trees.

Any suggestions, pointers and solutions are welcome as ever.

Ochimus