So far only the front passenger seat on ours has squeaked and only with someone in it.
Wiggling the seat back seemed to show the squeak coming from the tilt mechanism components/hinge on the righthand side of the seat ( offside, nearest centre).
I used 3 in 1 oil with PTFE spray, as I don't like using silicone sprays inside near trim, just on those bits.
So far, squeak gone.
Remember, with true bucket seats with contoured and slim backrests it is hard or impossible to fit side airbags,
Btw, I've also tied down the under seat tray by cutting slots in it and using releasable cable ties round the seatframe bars.