Advice what to put on black plastic

Hi,  Can anyone help?  I have covered an area of about 30 metres by 10 metres with black plastic for last two years (it was full of brambles and other annoying weeds), the ground is quite uneven and I have started to plant raspberry bushes and some shrubs here and there but I need to put something over the black plastic as it looks so ugly.  I cannot afford bark chippings for such a huge area, if I use sand just to cover the black plastic will weeds still grow?  I do not want to take up the plastic and lay grass as I already have a huge amount of mowing to do!!  I want to try to create something interesting but need to do it on the very cheap...any advice?  This is not on an allotment but an area of land next to a field.  Thanks!

I was thinking of grass cuttings but will they go all slippery once degraded given that it is on black plastic? Also will weeds grow in the mulch?  What if I mix sand and grass cuttings?  Will that just invite weeds?  Thanks

Hi I am in France, I do have a builders merchant nearby but I have used so much gravel around the place I was hoping for a 'softer' looking option for this area,  I think I may try sand mixed with grass cuttings then maybe add some gravel although I am worried that the sand and grass might encourage weeds to grow.

I don't think the grass cuttings will encourage weeds, but they will I'm sure try to come along through sand or gravel. You always though, have the option of spraying or watering weedkiller carefully around the raspberries onto these hard landscape materials.