VAT on Shipping for VAT free products

I sell mostly books which are VAT free in the UK but I also sell some vatable products. I have my shipping set up on a weight based basis. What I need to be able to do is set the cart up so that invoices show vat including vat on the shipping for VATable products but show no VAT for the VAT free items.

Currently I have the 'Taxes' checkbox ticked in shipping method screen and so my invoices show VAT on the shipping for VAT free items which they shouldn't. If I uncheck that box then my invoices for VATable products show too little VAT because the VAT on the shipping isn't included.

Anyone got any ideas?