I use two pence pieces, just the right width for a tile joint. Pull them out when the tile cement is set enough to hold the tiles. Works a treat and costs nowt
Mate of mine slabbed a floor in a posh house with stone and he used old pennies. grade something listed. Old skool way of doing it. So, good on you!
Must admit I was tempted to do the same, though I don't know what coin I would have settled on, maybe 1 French cent (100th of a Euro) as they are small, like an old half new pence piece.
The only thing with the plastic cross pieces is that if a tile isn't exactly straight for some reason you can turn the cross piece sideways on so that you put two legs in the gap, which is just a fraction wider than one leg used the normal way on.
Haven't explained that very well, but the cross section of each leg of a 2mm spacer isn't square, it's rectangular, which can be handy. Not all tiles are exactly the same dimensions and when using narrow grout lines, which do look so much better/professional, you sometimes need to be a little bit more fussy.
From the tone of some posts here I get the feeling that I am in a bit of a minority enjoying tiling.
I never get tired of having a look at the kitchen tiles while waiting for the kettle to boil!