deposits

hi there
can anyone help
i have just purchased a payment plan addon which isnt really doing what i require

i have a prop hire company http://www.the-sweetie-cart.co.uk what i require is for a customer to book a hire product for say £250
pay a £50 non refundable booking deposit at the checkout
and i can send them the invoice with if possible a £50 returnable breakage deposit
and i do free delivery within 25 mile so if i can ad a milage charge to the invoice like so
product hire £250.00
non returnable booking deposit received -£50.00
Returnable breakage deposit £50.00
over 25 mile charge 10miles @40p per mile £ 4.00
Balance due £254.00
for the balance a month before their event
or
they can log in to their account and pay the balance a month before their event