I got MEP yesterday, but my Bio also linked to the previous Bio for work permit, any no BIL or anything else.
When I was apply for EE, I also didn't have any idea how to pay Bio fee upfront. But just this morning I find the website to pay and then I paid and sent a webfrom with the receipt.
I think this will not do any bad, even they didn't get it from webform, I can still upload the receipt again to the system. Hope this will help you.