youve got to wait for the concrete to set 
Thanks for that Barry. It certainly makes a difference when you wait for
the concrete to set.
Anyways, now I've got the hang of it, I went to a large country house this afternoon
and it's surrounded by flowerbeds and lawns. It took me a while to lay all the concrete slabs where I need them but well worth all the hard work.
Even the customer is happy! Cos now she has somewhere to stand all her large flower tubs and all I have to do is move them when I clean the windows

I can't thank you enough for the tips you've given me. Everyone's a winner!