Check out with Spikings, he's the founder of the diving group here and went a couple of times. (glocals scuba diving group) - i think there are some plans of going soon.

I recommend staying at the following hotel: http://www.pizzovogorno.ch/en/

It is cheap, basic, bang in the middle of several dive sites, approx. half way up the valley and has an air filling station on site. The guy who runs the hotel also has diving contacts in the region, so he may be able to answer your questions better than I can.

I can't recommend any particular diving school because we dive independently. However, you may want to have a look at: http://www.maggiadivers.ch/

A few tips: it will be packed in the summer (we usually go in April/May), and watch out for sudden and strong currents, which can trap divers beneath boulders. You will need a rope (which must span the river channel downstream of the exit), and a carribiner, which is used to secure yourself to the rope should you be swept downstream of the exit point. These can be rented from any climbing shop in Locarno, or via the contacts of the hotel owner.

Have a nice trip!

I have a lot of rope if anyone needs one, also some old carabiners probably. 

Thanks for all the help guys.  Not been lucky this time with a response so unlikely to make the dive, I will continue to see if in the future I can find a guide.

Cheers