Shipping charges trouble

Hello all,

I’m having some trouble with shipping charges.
I’ve got some items on my shop I want to be Free shipping but I want others to be a flat rate charge.

I’ve set up a shipping class to apply a flat rate to the items I want to charge shipping for, but with Free shipping as an enabled shipping option I end up with the cart showing a choice to the customer so they can pick if they want to pay the flat rate or have free shipping.

Is there a way to have a flat rate apply to some items but free shipping to everything else?

Thanks