Aquadart shower dripping?

I had hoped that the instructions given would enable me to fix the dripping but when I removed the cover the shower mechanism was quite different. The copper pipes where screw fit not push on and the rest of the shower mechanism was covered by a plastic casing. I guess it is an older model? There was also a bar which looked like it held together the taps. I am reluctant to tinker with these in case they fly apart and I cannot put them back. Any help would be very welcome.