The agency I spoke to say I need to attend 2 appointments and only need to test for bike. Not car because I already hold UK and international license. And no additional docs needed. Fast track service is one week and one appointment. Time is money in my opinion so i'm happy to pay for an agency to save me all the additional trips and appointments I would need to make without one.
It doesn't sound simple enough for me if I need to get a residence cerificate and doctors report first. I know it's likely easy to get both but an agency saves me the additional trips and would be much quicker.