Holywood*,
From the pictures the quality of your retrim looks excellent. (what was the cost)
I agree there are certain advantages and disadvantages using leather or vinyl in different places and also the seat design has to be considered as to whether the covers are fitted over the foams like a sock where a vinyl backing is essential to allow some stretch or like the Lotus +2s where the wraparound is like an apron and the back fitted separately. The advantage of vinyl is it can be grained exactly like leather and the material backing can be varied to give strong rigidity or almost an elasticated weave which allows flexible trimming stretch on complicated contours or suspended headlinings.
I have either fully retrimmed or partially retrimmed all my cars apart from the Rolls Royce and Esprit Turbo which were just reconnolised.
Each was done for different reasons...........the Ferrari was originally all black seating and doors and a horrible black leather stuck on headlining. I fitted a glass roof in the removable top so as I could create a suspended headlining and much better for long journeys in case it does rain. The whole car was done in cream autolux with red inserts and piping
The MGB had been done by the PO although mainly leather the company had used vinyl over polyurethene cord for the piping and that just does not work as any slight nicks/damage cannot be repaired as nothing will glue together. I stripped the seats down and fitted leather piping over cotton cord so if the edge of the piping ever gets worn or damaged a perfect repair can be easily done.
Whilst my preference is leather faced seats and leather piping I could not find a leather grain that matched for the Lotus and the PO had been a smoker and there were burn marks on the drivers door, seats and centre console. I discovered MG used the same vinyl grain as Lotus so was able to pick up some old bits of material. I also used the seat backs and replaced these with a near match. This gave me enough material to sew in new panels where the cigarette burns were, so I avoided a complete re-trim. Albeit the carpet had all turned brown so this was easily replaced and at the same time I made myself some headrests.
Vxah.........10 skins at ?15 each is definitely a bargain and I would buy them even if not for car seat use they would always do the pipng and other areas. When buying complete hides you have to look out for scab damage usually caused by barb wire fences and also big scars in the middle of the hide where a cessarian operation may have been done years before.
Leather does not really have a grain pattern this is rolled embossed in to disguise many imperfections so make sure they all have the same pattern as there are many different possibilities of grain. Top quality automotive leather referred to as 'autolux' as can be seen on RR, Jaguars, LR, Astons etc is generally sourced from parts of Europe that don't use barb wire fencing so skin damage is negligable so the leather does not have to be embossed.
Having visited some of the old tanning sites I can assure you the smell is awful. Great article here explaining the processes.
http://en.wikipedia.org/wiki/Tanning.
One other tip is if you do have some 'puckers/ripples/loose spots in vinyl or leather it was part of the process for headlinings and seats when trimmed to place a tube into the inside area and push steam into the back. I have seen these devices made by DIYers just using an old kettle with a hose on the spout. Obviously we used to have a proper machine but the kettle works fine. The steam softens and relieves any tight areas and as the dampness dries the shrinkage is taken up by any loose parts and by the next day the seat will be nice an even. Works for leather or vinyl.
Regards
Steve