Percentage pricing by attribute

I'm not sure if this is possible - I've spent a good couple of hours reading a LOT about attributes, but not stumbled across anything like my specific situation, and yet it seems to me as if it should be quite simple.

What I have is:

Display Counter in several widths, at a different price per width

Several finishes (3 plain, 10+ woodgrain) where the plain are no extra and ANY woodgrain is 20% extra.

So

Width 1= 330
Width 2= 360
Width 3= 430

any plain finish=0 extra
any woodgrain=+ 20% of the price by width - so +66, +72 or +86 as appropriate.

Can I do this by attributes or do I need to create separate products for each width?

And if I can do it by attributes, is there a way to make the label show (+20%) rather than (+££)?

I've played around with price factor and only seem to be able to get it to operate on the lowest price.

Price factor was meant to work against the products_price ...

Example: products_price is 10.00
Color red is 80%
Color green is 80%
Color gold is 120%

Now when products_price goes up to 12.00, the attributes that are set based on Price factor automatically adjust ...

By default, it can also work against the lowest price on a Product set to Price by Attribute ...

It cannot, at this fime, flow with the change of the price based on the attributes changing on the fly as the Product is built as then the calculated Product Price is changing vs a fixed price that the display uses ...

So that's a "No" to "Can I do this by attributes?" then? :laugh:

For anyone else with a similar problem, my workaround for this is to create 2 products using the finish (ie plain or woodgrain) as the criteria and offer those in the different sizes priced by attribute. A logical progression from this was to then split the "Counters" category into 2 sub-cats by finish, leading the customer (hopefully) straight to where s/he wants to be.

The other option was to create 6 products according to size and then price by finish. This is more cumbersome and doesn't look so good.