Ok, had a go at step 5,
I added a third recordset as follows:
Name: Recordset1
Table: productoptions
Columns: All
Filter: ProductOptionID = Form Variable - ProductOptionID
Then in my Add to Cart bindings I set the Size column to <?php echo $row_options['size']; ?> and my PriceIncrement column to <?php echo ((isset($_POST["options"]))?$_POST["options"]:""); ?>
I then added a calculation for RealPrice:
[PriceIncrement] + [Price]
and changed Price to:
[PriceIncrement] + [Price] * [Quantity]
Now the cart page is taking the PriceIncrement from the size option that is selected and then adding these to to give a RealPrice which is displaying in the Price column. However one thing I can't seem to do is get the Size that is chosen to display in the Cart details? Have I done the above correct?