clean and maintain cobblelock driveway?

Hi,
I got my driveway cobblelocked about five years ago. There was weeds etc growing through the cobblelock stone. I got a chap to clean it recently. He used a powerhose and he brushed sand between each stone. The sand was ordinary builders sand, I think. Now gaps have appeared between the stones in places. Firstly was powerhosing the best way to clean the driveway? Secondly is there special sand that is used between each cobblelock stone? What is the best way to correct this now? Advice please?

If you have a look on www.pavingexpert.com you should get the appropriate advice.

Run the search option in this forum also and there are a previous threads on this subject.

The sand that should be used is silica which I understand is quite expensive.