Hi Penfold,
Do I know you?/ you know me?
I came across Hydro optic about 4 years ago, they appeared to make or sell all sorts of diving equipment from regs,BCs, funny clips and masks. A dive shop near me seemed to be doing a roaring trade in their gear. They started doing a special offer, buy some of their equipment, say a knife, and then you could buy for a special price a BC and their Reg for £300.00 or there abouts.
The first stage of the reg looked (inside and out) just like an Apeks/Diverite/Zeagle clone the 2nd stage was like any simple plastic adjustable 2nd stage.
The diving shop closed and the owner left not only the country but also a large group of Padi trainees that had all bought Hydro optic regs and BCs but then wanted me to service them.....
I made enquiries trying to find the firm, head office, anyone who would speak to me, the closest I could get was a telephone number on the south coast of England that was never answered and an address that didnot return my written letters. As there was at that time a lot of divers wanting their regs servicing I wanted to do the manufactures course and open an account to get hold of the spares.
If you want to continue the search, best of luck, I suggest you try one of the registers of firms or SITA (scuba industry trade association).
Best of luck
Brian Cooper