Hi Gino,
From my time (62-79) and as I recall:
Nos 1s - Full Blue, blue collar, gold badges with or without medals
Nos 2s - Full Blue, blue collar with red badges (also the Duty uniform without blue collar)
Nos 8s - Blue shirt & Trousers Action Working Dress
Nos 6s - Full Whites with or without medals white or Black shoes
Nos 6As - White Front and white bells
Nos 10 - Blue shirt, blue shorts, black long socks (stockings) Black shoes
Nos 10A - Blue shirt blue shorts sandals (or no shirt if relaxed)
And, yes, we had a centre crease on the white fronts.
The blue collar had three creases (blue side out and not the mottled/striped under side) - there was coloquillism for this, but it is a bit on the rather risque (if you think of the female attributes you'll be close enough!!)
I presume the new shirt is for standardisation these days - you wouldn't need as much cash grant when you are promoted from Junior to Senior Rate. Strangley enough, I was in Pembroke in the 70s when they ran an initiative for the 'new' german style uniform (as Mountbatten remarked when he inspected the parade)for JRs (4 button double breasted), whereby they could save money in the same way - as it was they opted for a total crappy looking thing which I fortunately did not have to wear !!