Lidl today and spotted a grass mat for £5.99, so grabbed one with view to using it as a gaming surface. The size is 100cm x 200cm which is ideal for 6'x3' table.
Unlike most modern grass mats this one makes no attempt to have false blades of grass, but instead is more just a green, felt-like surfaced carpet.
When viewed from the top you can see small marks over the mat, I presume small holes for drainage again.
The colour is quite a deep, if slightly variated, green. Additional colour might be desirable for a more natural finish.
I'm pretty glad I bought this. It has a nice heavy feel to it, is UV resistant so should fade and was nice and cheap.