My DMP and hospital also required cash for the whole procedure. As stated make sure you have the required photos and forms with you.
For me it took a month to get booked in with the doctor, then after making the appointment they referred me to the hospital local to them for xrays. They were very good at 'trying' to get me in the same day! Luckily they were private so not very busy.
For the doctor i waited about half an hour and about 15 mins with the doctor. It was asked for me to take a urine sample with me to speed up the process (so no need to do it there) then he checked my eyesight, weight, height, blood pressure, chest, reflexes etc. I was asked to roll the top of my pants down and shirt up to allow him to check my hips/ribs/bits in between etc but no actual undressing. Then he took a blood sample (eventually!) and was very good about my fear of needles. I also had to answer some basic medical questions, was i taking any medication or doing drugs, that kind of thing. He then shook ym hand, wished me good luck with the visa and told me to pay downstairs.
When booking for the xray, they guessed the doctor part would take 3(!) hours so i still had a lot of time to spare, so when i gave them a call they managed to move me forward to slot me in. I waited for about 15 mins for the xray person to come off their lunch, was told to fill out my actual doctors details, then was taken to change into hospital robes for my top half, did the xray and was off on my way home.