Good morning,
I come to you for your opinion.
I added this vehicle a few days ago:
https://www.imcdb.org/vehicle_1937767-Gordon-Murray-Automotive-T50-2023.html

The make of this vehicle is "Gordon Murray Automotive" which sells models "T.50" and "T.33".
https://en.wikipedia.org/wiki/Gordon_Murray_Automotive

Looking at the site, the brand "Gordon Murray Design" also exists.
https://www.imcdb.org/vehicles_make-Gordon+Murray+Design.html
https://en.wikipedia.org/wiki/T.25

Should the two brands be combined under the "Gordon Murray Automotive" brand or should they be kept separate?

On the DVLA site the GMA is registered under the make "GORDON MURRAY AUTO", so I assume that having it listed under the "Gordon Murray Automotive" is correct, as they also seem to use that name on their site as a brand, not just as a company name.
About the Gordon Murray Design vehicles, it would be interesting to find a registration (the O56LB is not found on DVLA site) to know if they use that name or if they are also registered as Gordon Murray Automotive. They use a similar model name, but from Wikipedia I would guess that they are a separate brand/make, possibly they are older and they changed from one to the other at some point.

They're trade plates, similar to our Z-plates in Belgium. The black T25 had a standard british plate once, T25 GMD, but I've found nothing on plate check sites.

https://i.ytimg.com/vi/h049hLF2fVY/hq720.jpg?sqp=-oaymwEhCK4FEIIDSFryq4qpAxMIARUAAAAAGAElAADIQj0AgKJD&rs=AOn4CLBkhbCFVM3-mfr0QSKlNM9EDSq6uw