You can go and see a Concorde at Bristol Aerospace Museum[0], and walk inside it.
There is an absolutely bewildering array of dials and switches exposed to the pilots[1].
And they have lots of other aviation stuff at the museum, it's not just Concorde. Other highlights include some very early planes, cut-away jet engines, and a cut-away section of a jumbo jet fuselage, so you can see the locations of pipes, tubes, cargo, etc. in relation to the seats. It is well worth a visit if you're nearby.
In period, it was not that snug. This was in an era when you could get a dozen people into town in a 2CV and the majority of adults smoked. People were a lot leaner then, and considerably shorter.
In 1954, in the UK, the average male was 5'7" and 11 stone, 6 lbs, which equates to quite a high BMI of 25 (18.5 - 24.9 is healthy BMI). Nowadays there are very few men in the UK with that weight. Let's ignore women from this because women were second class citizens at the time. Men are on average 2 stone heavier.
But average weight is just average, nowadays with 2/3 of UK adults overweight, there are far more people at the top end of the Bell Curve, at double the average weight people had on the 1950s. So half of today's population would not fit in the seats.
When you look at old European or Japanese cars such as the MINI or old FIATs, bear this in mind. Those cars might not have ever been spacious, but, in period, they were not cramped. Similarly, Concorde was never spacious, but it was not a very snug ride until obesity got the better of us.
I think that there is a reasonable argument that half the population don't fit in today's plane seats. Also, it isn't always weight related. My BMI is low 20s and I'm quite tall. I can't put my legs together, as the seat in front is too close.
I hate flying.
A relative who used Concord a few times didn't comment on the space, but instead said it was the noise during flight that meant he preferred British Airways first class on a normal plane, if time wasn't essential.
Looking at weight is overrated. Unless you're actually massive it usually doesn't matter for space at all.
My BMI is over 25 but yesterday, in a normal train, I could hardly use my large laptop because my arms are long and my shoulders are wide. My ass fit into the seat without any problems. Also surprisingly, legroom was good.
When the Concorde flew, the panels would expand. On the last flight of the one in Seattle, one of the crew stuck their hat in one. When it slowed down, the hat became stuck in the wall. It is still there.
The 737-100 (and maybe the -200?) had a similarly busy cockpit, as the first examples were built when flight engineers were still required. Avionics simplified a lot since then, but the Concorde program died before it could get similar treatment.
There are two in Toulouse, one you can walk into (the first prototype, actually). The place is called aeroscopia [1]. There's also an A380 prototype and a bunch of older planes.
You can also visit one in Germany at the Technik Museum Sinsheim[1]. It has the advantage that it can be compared to the soviet counterpart Tupolev Tu-144 that is also exposed.
And (at least) two in Paris. One mounted on stilts at CDG2, which depending on how you taxi you may or may not see from the plane, and one just outside ORY, which is maintained by an association, and visitable.
I lived right at the end of the runway there in Bristol and Concorde needed the whole length to land, so it would come in real low and shake all the loose stuff upstairs.
There is an absolutely bewildering array of dials and switches exposed to the pilots[1].
And they have lots of other aviation stuff at the museum, it's not just Concorde. Other highlights include some very early planes, cut-away jet engines, and a cut-away section of a jumbo jet fuselage, so you can see the locations of pipes, tubes, cargo, etc. in relation to the seats. It is well worth a visit if you're nearby.
[0] https://aerospacebristol.org/
[1] https://i.redd.it/0vqv9qlx98m31.jpg