At some point my dad said he's sad we didn't keep the drivers seat as well.
Essentially all these seats go for scrap so you could get the leather seats from a 7-series BMW to have a mega cool sofa at home complete with arm rest and cup-holders. With a few more bits of wood you could make some outer arm-rests. Heated/cooled seats could be nice too.
Maybe there is a 1990's sweet spot where the electronics aren't present so adjustment can be done with mechanical controls, as per your Astra option. A Transit Van could have particularly good pickings with the right vintage.
Nah, I haven't watched any Top Gear. But the seat was just always so comfy in a way none of the seats in the never cars I've been in was. I think it is due to how the seat envelopes you, in a way reminiscent of race cars (which the Astra was not, by any stretch of imagination).
I think heated seats could be possible as well, I assume the required electronics and the protocols they speak for regulation should be rather simple. But given the seat is at home there is not that much need to heat it up :)
There was a company that sold a frame for doing just that, but they went out of business. Fortunately, you can still easily get all the attachment points/latches and such, and welding up some simple legs and whatnot isn't that hard.