Rockeries look best if you can use layers of rock that look as if they are just protruding from the ground. Don't just heap up a load of stones. Look at some pics under 'rockeries' for ideas. Also, it's difficult to make a rockery next to a pond look like anything other than 'where shall we put the stuff we've dug out'!! Check the growth sizes of any plants that you would like to grow. Some 'rockery' plants are thugs and can take over quickly. Avoid Sedum acre and 'Snow in Summer'.

thanks i will try to make it look something but havent really got green fingers

And don't add the concrete to your rockery... you need natural stone. A good rockery is a work of art, takes years to bring together fully and needs a lot of care and attention to keep weed free and the plants looking good.

My rockery ajoins my pond and looks great coming down to the water, but ditching concrete into it will not work nothing but weeds will grow. Bite the bullet and get a skip etc. The point of a membrane is to suppress weeds if you clear the area first digging out any perennial weeds a membrane will not be needed and the soil on top will seed weeds anyway. A rockery is supposed to look like a natural land scape so your rocks should be 2/3rds buried and the grain running in the same direction. The other idea is a scree garden?

may i ask what is a scree garden

Scree is found in mountainous areas. It is bits of loose rock, stones etc broken down over many years in which plants grow. It is best to make it on a slight slope and I have one coming down from the back of my rockery. I think they look better than most garden rockeries as the stones are more natural in their random sizes/siting. The bigger stones are at the bottom and it gets small/finer toward the top. Creeping alpines do look good in it and hold it in place.

Don't rely on weed membrane. Remove all weeds and roots from the soil you use, and thereafter the only way to keep a rockery weed free is to keep on regularly hand weeding it.
They are quite high maintenance. But they are lovely and worth the work.

thanks for all your advice ther is a lot to think about