A C1 medical will set you back around £350. Add onto that any travel expenses involved and it's suddenly quite a lot of money to spend on something that you will only need if you're lucky and get on the course. Above is correct, you don't need one when you apply, but you should read the CAA website on the level of health required and make a sensible decision on whether it's likely you'd be able to acquire a C1 or not. I'd imagine most people who can't get one fall down on the eyesight part. If you are fairly young with no serious health problems and have half-decent eyesight then you're probably going to be completely fine in this regard.