I still have the original sales literature for the Sydnope Scale Models 'Coronation' set.
These were a limited edition release of 75 sets, 50 sets sold as kits and 25 sets pre built. At the time Sydnope had a shop in Crich, Derbyshire (just down the road from the tramway museum). They had these built and painted coaches on display on their stand at the Derby Model Railway exhibition in 1984, the price for a built set of 9 coaches was £720.00 ex vat and £172.50 inc vat in kit form. I purchased one of the 9 coach kits, but later sold it when Dan Pinnock released them in nickel silver as these were far better dimensionally and the castings for the bogies etc were again far superior. The D&S kit sold at £250.00 at the time of the limited edition release albeit without the Beaver Tail Observation coach. Fortunately I kept mine from the Sydnope set.
The original Sydnope kits had cut to size and formed brass sheet for the roof on the models (certainly in the kit I had and as stated in the sales info.) so I suspect that the aluminium extrusions stated in this thread are probably non standard to the kit.
A year later (1985) Sydnope also released the 7 coach Silver Jubilee Set and the LNER Tourist Stock coaches.
A few years later Sydnope seemed to dissapear, certainly the shop in Crich closed and I no longer saw them at the exhibitions they had attended.
As I am sure most will know, there was also a Silver Jubilee set (designed by Rupert Everett Brown) and originally released by D&S, now available from Wizard Models (in Nickel Silver). They are also available in 7 or 8 coach variants from MARC Models in etched brass. The tourist stock again designed by RDEB were available from D&S but can now be purchased from Wizard (in etched brass).
It is unlikley there will be any further production of the D&S Coronation sets, but I have seen 2 sets crop up on that 'renowned' auction site in the last couple of years where they sold for high prices.
There was one other supplier/manufacturer of etches for the Silver Jubilee Rake that were discussed on Model Rail Forum a few years back but I forget the concern responsible.
Then of course there is Coopercraft but I won't go there.