TheRailwayCentre.com (now defunct) used to have these, and the good old Wayback Machine has them archived:
Check out the single cab Class 58!
Excellent link, cheers for that.
The Class 157
Strathclyde Sprinter and this one of a Pacer (numbered 142001, but looks more like a early 143/144 mockup in terms of overall body shape) screened up for Oban are the ones that interest me the most as far as DMUs go:
The mockup of a proposed Class 314 interior refurbishment is also interesting in that it
did become a reality, at least in part. The ex-Class 507 DMSO* (64588, originally numbered 64426 when part of 507022; the latter being written off in a collision with 507004 at Kirkdale TMD) that was became part of 314203 (one of the units involved in the Newton accident in July 1991 and whose original 64588 was completely destroyed in the crash).
When 314203 finally emerged from it's protracted rebuild in 1996, the 'new' 64588 had been fitted with a experimental interior of sorts (see middle attached image below, copyright of Matty P) that no doubt drew influence from this concept (the door vestibules primarily), everything else remained consistent with the rest of the 314 fleet interior-wise at the time. Contrast and compare the concept with the real thing, both pre and post-refurbishment in 2011 (last image copyright of the Scottish Trains Website).
It's really a pity that more wasn't done with this concept - there's every chance that there were plans for it's like to be perpetuated across the entire 314 fleet, but was ultimately dropped on cost grounds. This is pure speculation on my part I'll admit, before anyone starts aiming for my jugular lol - as it would've kept the 314s feeling at least relatively fresh throughout the 2000s (or left them feeling even more dated, depending on who you're asking) and would've been given a 'Saltire' refresh in 2011/2012 to see them through to 2018-19. All academic now of course, but even so. A man can but wonder...
*: short for Driving Motor Standard Open (including this just so I don't get collared for citing obscure railway/rolling stock acronyms lol).