Hi, there ... my wife and I used the Premium Service available at our nearest PEO (Glasgow) in 2011 when she applied for ILR. Process was completed in less than 2 hours and I highly recommend this method - providing you follow ALL the instructions in the guidelines. Full fee is payable on the day of your appointment.
Yes, they do ... ours was paid by Visa Debit.
Hopefully our experience offers the reassurance you're looking for ... and I wish you the very best of luck with your application.