I had a problem with the driver's seat on my x-type towards the end of our relationship. The seat bolster split along the stitching on the door side. i took it to my local cobbler - he stitched it and then used a creamy dubbin type stuff which worked a treat.

It made me think - for 30 ish years when it was important I polished my shoes/boots every day, using fair amounts of polish/conditioners. I had never once thought about the car seats.

After that I used various stuff, from cheapo leather furniture polish to special car seat polish but mostly Kiwi black shoe polish and it made a lot of difference to halt cracking, feed the leather, etc. I'd try that first.

If you check youtube you'll see that there are specialist detailers who can deal with leather, filling cracks, restoring colour, etc. They seem to get good results but i've no idea what they cost.

I think it may be worth getting the stuff they use nowadays on walking boots (the modern equivalent of dubbin) and having a go. Feeding the leather to regain the suppleness id the first aim, then dyes etc. are available to restore colour.

Thanks everyone. I’ve investigated swapping the seats over and because the seatbelt mounts are part of the seats, I don’t think it is. I got to know how the seats go together very well when I fitted the current ones as I had to swap the rails over.
Also, after much hunting online over the weekend (when I was feeling rotten after having my first COVID jab-but luckily was okay for my Sunday service in church!) I’ve found a pair of cloth seats for £100 on eBay. They were wrongly listed as leather, and my offer of £100 was accepted (listed at £130). I might even sell the old pair and get something back!