Surcharge for certain payment system

Hi,

Perhaps someone can suggest an easy way to do this.

I wish to add a surcharge on to one payment system (namely Alertpay) Eg; for every order I would like to add GBP £0.25 as a "fee" or "surcharge" for using this payment method but not for using any of the others.

I did manage to make a very crude system but for some reason it required me to add 0.31 in the alertpay processing page to get it to add 0.25 when they got to the Alertpay site. I also had some issues with adding a warning when paying by alertpay in the checkout page that a 0.25 charge would be added, worked in all languages but caused french to get a header output error.

So if anyone has an easy way of 1) adding a 0.25 charge to payments made by Alertpay and 2) notifying clearly to the customer that this charge exists before paying then I would be most greatful.

Regards

Anyone any ideas on this ?