What to expect for a class 1 medical?

[sppl_James]

Hi my name is James, I am 19 and currently studying towards gaining my PPL with a burning ambition to one day acheive a ATPL.
At the moment my flying instructors are suggesting that I should go to Gatwick and try to get a Class 1 medical.

I really would like some advice on what to expect when I get there? How they do things? What they need to know? etc.

I dont think I should have any problems because I keep myself very fit.I dont smoke and drink very little.

Thanks for reading this far and for any replys I get

James.