Payment Processing Fee For Service Products?

Most people pay for my photoshoots using email to arrange a shoot and then bank transfer, but for those that buy a photoshoot direct on my website and use Paypal, I want to add a processing fee ('shipping').  I can't seem to get this to work though.  I guess because it is a 'service product' maybe?  I have the shipping group set to default, and as far as I can tell there should be a shipping fee applied, but nothing is showing up at checkout.

If I can get the shipping fee applied, I'd also like it to say 'Processing fee.'

Have I missed a checkbox somewhere that is preventing me from applying a fee to service products?

There is just not a way to do that. The shipping won't work because it is not a shippable product. You could  just work the additional cost into the price of the service.

Ok, that's a shame.  At least I know now that I haven't made an error somewhere.

Many thanks.

I did think of a possible workaround. You can create an option for the service product like in the attached screenshot that is required and will add a fee to that service. 

Oh that's great, the perfect solution as I can change the fee amount individually and according to the value of the service.  Brilliant, thanks.