Building an 'Order Online' site

[#1]

I'm hoping someone can point me in the right direction.
I've built a PHP/MySQL site that enables our trade customers to login to their own space and construct an order by product selection followed by a series of extras. i.e. They choose a window style and then specify sizes, colour, glass, delivery etc.
What i need to do now is allow the user to enter his credit card or PayPal details so that he can place the order with us.
I don't want a shopping cart as such but i do want the buy-online feature that shopping cart software provides.
Do you know of any 'off-the-shelf' PayPal or Credit/Debit card processing packages?
I've never done any eCommerce so I don't know where to start

[#2]

Have you got a a merchant account and can they help?
If not what about  https://www.paypal-business.co.uk/website-payments-pro.asp

[#3]

Thanks for your reply itsme.
We are just going down the route of getting a merchant account but because I'm not involved in our accounts dept I'm a bit in the dark.
I have been looking at PayPal options and I can see that there might be a solution there but again I'm a bit in the dark about the company's financial arrangements.
As I am learning though if they want me to build this then they have to give me more info!