I expect foam mats are deemed unsafe because they can be chewed. Any normal material playmat will be absolutely fine. They are all a little padded and that is enough, even on a wood floor. I wouldn't put anything else under it like a duvet etc, just because once they start to roll you don't want them falling asleep face down on something their face can sink into.
As for educational, again any playmat with a couple of dangly toys and some bright colours is educational for a baby, it is just about discovering different textrures and working our how to grab things so you don't need ot spend a fortune on some brain training baby einstein gubbins.
What do you mean by educational? Honestly, your baby won't learn much from a play mat
Get a nice rug which you can lie baby on and some toys. Baby can lie on their front (good to build muscles) and look for a play arch for when they're on their back. Baby will be rolling etc by 3-4 months so no need to waste money on anything fancy.
I am currently pregnant and although a little early, would like to buy a playmat for the little one- an educational one that would double as cushioning for hard wood flooring. I think this was sparked off by me seeing a colourful alphabet one in John Lewis. However, I have been reading that foam mats are unsafe. Any recommendations as to where I could purchase a safe one from please?