Just butting in here (totally uninvited, but relevant)....
...Sorry to be the bearer of 'bad' news - but, hey, acurate information is usually a good thing!...
...the brakes you have fitted are NOT a 'big upgrade' (usually referred to as the Vectra upgrade), but there is still an advantage to be had.....
Starting at the begining, the numbers stamped into the caliper (KBA 60298) suggest that they are OE fittment for an Astra 'F'/Nova GSi - see
here....
These use then same disc as the elan - Apec Part number DSK518 (and other equivalents) - with a diameter of 256mm.
The Disks you have in the picture are some aftermarket drilled/grooved items, (designed for the Vauxhall, but equally at home on an Elan - or even a Daewoo Lanos), so they should run slightly cooler than solid ones (not that I'd expect to notice the difference).
The 'proper' Vectra Upgrade uses different calipers (as fitted to the V6 Vectra, not the lower models), with a larger disc (OE for a Subaru), and some extra mounting hardware.
The clues are:- The disc will have extra stud holes in it - they originally get used on a car with a 5-stud pattern, and need to be drilled for the Elans' 4-stud hubs.
It will also be larger in diameter (I believe that it uses something like 288mm, but that is only from my poor memory - I've never owned the kit (except for on my Vectra, I suppose).
The calipers need to be mounted further out from the hub to fit the bigger disc, and so a 'new' mounting bracket needs to be made up.
Anyway, enough of what you don't have - what about what you DO have.....
The ATE brakes were considered by GM to be better than the standard ones (otherwise why reserve them for the 'high end' models??) - and as such, *should* be better than standard Elan calipers...
This is for a few reasons - the pad position in the calliper is slightly further from the hub (disc is cleaner on the outer edge), so dynamic rotational physics dictate that for the same force at the brake pedal, there will be more force at the disk (everything else being equal)...
...the caliper uses a different brake pad - which has a slightly larger surface area in contact with the disc - so has to be better.
There is a much larger choice of brake pads availlable - all designed to stop a big, heavy Vauxhall (same pads on an Omega) from 155 mph, so should be good for an Elan).
It still has the Achilles heal of being a single-piston calliper, with sliders, but the good news is that the sliders on these callipers are less prone to seizing up...
Basically, it is an improvement (maybe not an upgrade), using easy to find parts which will make life a tad better.
If someone were to replicate the system today, it would cost about £50 for a pair of S/H calipers (which may need a rebuild), then a set of pads, then new discs.
So it could easily cost you well over £100 (depending on what you can find/do yourself) - for a small but maybe not worthwhile improvement (but every little helps
).
With other options available which are definate upgrades, I wouldn't bother.... (maybe one day, if/when I can no longer get pads i like for the OE Elan callipers)....