How do you enable payments for your startup that is not backed by a big company?

Who do you use for processing online payments for your side-projects? (in Europe)<p>I am working on a side project, that is to validate an idea I have about a product. I have a fairly good solution on how to validate my idea, without too much programming.<p>I believe that the only way to validate my idea, would be to ask for credit card information and process a given amount of money from my potential customers. I don't know any other way to be sure that people would be interested in a product.<p>So considering that the product is not yet ready, and I am about to setup a small marketing website, how do I approach a payment processing company? (Recurly, Spreddly, Wirecard or any other payment processor in Europe). I don't have any history of successful businesses, and all these companies are asking for "expected number of transactions", "expected revenue", etc. Unfortunately I don't have such information.<p>Furthermore all these companies expect a minimum payment of about 100 euros per month.<p>How do you enable payments for your start-ups that are not backed by thousands of euros/dollars?