Remove tax Paypal standard

Hi,

I want to give my customers a 'price you see is what you pay' experience, so I have added a sales tax code and setup a value of 20% (UK VAT Rate) and that works great the customer see's the product price including VAT and the price excluding VAT, the problem is that because I have several other sites that do not add VAT until the customer logs into paypal (because thats how they are currently setup and cant change that just now) then paypal adds VAT again..., so what I would like to do is remove the VAT that has been added by Opencart from the paypal module when the confirm button is hit so that the VAT is not duplicated by Paypal.

Regards

mark