Wizzel, I think the older ones are fine, you just need a bit more care cleaning up parts, and sometimes a bit of strengthening of joints, particularly wing to fuselage and tailbone to fuselage. A short length of brass rod does the job. They are really nice kits of cool subjects though so get them made.
Brid lufc - the plastic is about the same as the stuff new Airfix are using in my opinion. The parts are best cut from the runners with a fine razor saw (and I mean a razor saw, not one of those chunky miniature tenon saws I used for years - see pic below of my small collection of saws, the razor saw I like best is the wooden handled one), but they clean up fine. The detail looks a little soft in the close up photos, but don't forget these models are pretty small and the camera lens was very close. Not tried an A Model, are they OK?
I have also included a photo of the clear parts. I have painted the clear Zephyr parts with black acrylic on the edges to reduce internal reflections. Hopefully you can see the difference between the treated Zephyr parts and the unpainted Magister parts on the same sprue.
Happy Modelling,
Roger