Rossco;
EGDR summerised the medical pretty well. If you're booking it now you'll probably get a appointment for about this time in October; thats the time scale mine was in when I booked it in July. BUT there is no question do the Class 1 if you intend to train for an ATPL and find out if your ok.
As for height/weight, unless you are at one of the extremes; i.e. fat/short or thin/tall you should be alright there - but I don't remember them doing that with me. BTW I almost nodded off during the epilepsy test, she saw the readings enter a very relaxed state and she started talking to alert me!
BTW: BTW means Between the words...
The only thing I questioned were the eyesight requirements, so I took a sheet to Boots and had an eyecheck before booking the Class 1; after all £20 is much less than £400. If there were anything serious that would fail you you'd probably know it in the back of your mind.
Hope this helps!
SS