Standard seat back removal

[Madmaninshed]

Hi, I know this has been covered before, but I need to replace the foam in both the backrests of our standard 1986 seats, which have head rests but no arm rests. At the same time, I would like to wash the base and backrest covers, and thoroughly clean the seat runners and mechanisms, as the seats are so gummed up that they will not slide forward anywhere near enough to remove them, even after lubricating. I can’t even get them close to where the safety catch needs operating. The passenger seat (only) has a swivel base.
i have the new foam, but am having difficulty in taking the backrests off the seat bases. Because I can’t get the seats out, I’m having to work with them fitted.
I saw a post from 2022 which states that you can remove the backrests off by removing the 2 large Allen key bolts on either side of the seat, removing 2 smaller Allen key bolts under the seat rails, and by prying the spring bar out.
I cannot move the spring bar, which seems very firmly fixed, and I cannot find the 2 smaller Allen key bolts under the rails.
Any thoughts would be much appreciated, as I am struggling.
Many thanks, Paul.
 

[Rik]

We did this a few years ago. Can't remember the exact details but it was an annoying job. Don't think we really got the seat base and backrest to separate, but at least to lie flat on the floor. That gives enough space to work on the cushions.

I vaguely recall that it took a lot of force to get the spring out of its retaining hole, after which it slides to the side quite easily. There are indeed some allan bolts (where exactly i cant remember). With those out and the spring out the seat can lie flat. Sry I cant provide more detail.

Don't know if you can see it, but this is the only photo I can find of it:

[Madmaninshed]

Thanks Rik,
I will give the spring more force. I was worried that it would break.
If anyone knows where the other smaller Allen key bolts are, I would be grateful.  As mentioned, sadly I can’t seem to get the seats to slide anywhere near forward enough to get them out.  In fact, trying to do so, I thought I had got the drivers seat completely stuck with me in the seat pinned behind the wheel!!
 

[Madmaninshed]

Quick update - Got passenger seat out with a rubber mallet. Boy was it gummed up!! Found the smaller Allen keys under the runners, pulled the long spring out, and separated the seat base from the back. It seems that the job can’t be done unless the seats are removed. Having bent back the retaining spikes, I removed the cover, and found a horrible mass of powder and old wadding.  I cleaned everything, removed the long thin metal retaining rods from the cover, and washed the cover several times. Then I fitted the new foam back, which wasn’t tall enough to fit from the seat back top to hook over the bottom.  I had to leave it unhooked, and hope it won’t cause a problem. I will now try to reassemble the seat, but have two metal parts (now kindly identified by a member in a parts diagram), but need to figure out how they fit.  Seat back looks great, and hopefully will be in use later today - fingers crossed!