Can't / won't argue with any of the above. I can only draw on how I wore kit and the way others did, in the period I served but also having read and collected a lot of books and mags on the British Army since then.
In NI during the late 70's we were issued the shirt KF, which was hated. I used to shave the inside of the collar so at least you didn't get friction burns. After a while I bought a few US Army green long-sleeved shirts which made life a lot more comfortable. We couldn't get away with wearing No 2 Dress shirts as these were for NCOs only.
Jackets were tailored, not to excess but so there wasn't a bumful of material to fold back when wearing your webbing. Of course in those days we had better shapes to tailor to....
Berets....a thousand different looks, in time you could tell someone from behind by the shape of their beret. I wore mine (and still do, on occasion) with cap badge directly over the left eye but with the beret headband right on the eyebrow. The back sat right at the crown of the head, not pulled down like a condom. Working in a 'temperate' climate meant that the beret got soaked regularly, shrank and dried on your head so fitted very well. If you could throw your head around, leg it across any sort of ground and the thing stayed where it was, then you had it right.
Wearing DMS boots with puttees, they were worn the usual way but not with the 'trollies' inside the puttees. We wore cut-down braces with the metal adjusters, or bought the 'blousers'. These were set half-way on the puttees and the trousers folded under them, you then stamped your feet to get the trousers to 'hang' properly. By the way, if you ever see a bloke doing this anywhere (like getting out of his car) then he's probably a veteran and you know why he's doing it.
When we started wearing NI Patrol boots or Dr Martens, it was pretty much the same drill but the elastics would be set near where the lace was looped around the top of the boot, and the 'stamping' ceremony continued.
As Fred says, regiments and corps had their own styles for berets....tankies / armoured wore the badge right in the middle of the forehead, with the beret folded down on both sides instead of the right. This I believe is due to their regular use of headsets (any excuse). The Paras...I was told it depended on which battalion it was - 1 Para wore theirs over the eye, 2 Para slightly to the left and 3 Para half-way between ear and eye. 9 Para Eng Sqn RE wear their RE cap badge half-way around, almost hidden by the beret (maroon). I worked with blokes who were ex-Royal Irish Fusiliers / Rangers, and they shaped their berets like the caubeen they used to wear.
If you turn up any photos that need discussion / explanation, put them up. Loads of scope and the parameters are very loose.
