A little tip i was given when using the jigsaw ,use at full speed with a blade that has a lot of teeth the fewer the teeth the rougher the cut.

amazing how much difference platforms make, found with mine (Metcalfe N gauge kits) it made a huge difference. even with the rest of the layout being utter pants for reliability it looked better while on a technical level what you have is quite crude I suspect once you stick a bit of basic weathering on, have the ballast done its actually at normal viewing distances going to look remarkably good to the human eye, throw in a moving train and the eye follows the trains - which its already doing here at which point the platforms even as they are now look very good and have made a massive visual difference. one point I'd note, keep something to identify where any screws in the structure are, just so if you decide to add platform lights you don't try to drill through them

I'm running N scale and I was considering making my station platforms from balsa wood, both my platforms are curved. BUT then I discovered Peco NB-26 Platform Edging - Brick type. Thank you Peco 👍

great work and progress and lot of problem solving with the ramps

Rather than a ramp, you could just put a set of steps at one platform end, maybe the other could terminate with a metal rail. The main reason to include ramps is to allow track level crossing, but you have a subway, so carts can cross platforms that way, if you have a ramp at each end of the subway! You could skip modelling the subway on the nearside platform by hiding it under a station concourse - waiting rooms, cafe, news stand, WH Smiths! You could include a lineside hut at the bay end of the platform. And maybe a solid buffer-stop on the platform at the end of the bay, with a sand-trap to stop runaways.

You have a nice bit of space look forward to see your layout develop. Try do a couple of levels my mistake at tge start was mine was to flat.

As for your binding issue with the Mk3 coaches, you could do what they've done at Birmingham New Street at the crossovers - shave a little bit of the coping stones on the platform edges.

Coming along nicely. I think it's OK but just try a Mk3 coach on those points near the end of the platform. Just to be safe.

Regarding your problem of platform clearance from your Mk 3 coaches, instead of shaving your platforms down why don't you just pull your track over 1 or 2 mm. Also re your rough jigsaw cutting problem it is because jigsaw blades cut on the up stroke, you can get blades that cut on the down stroke like most saws do, which will give you a neater cut.

Little tube of polyfiller would have done the trick.