Yep - it's called an angle grinder - once it's in bits throw it in the bin and install one that doesn't have so many parts to go wrong.
Seriously though, that thing just looks overly complicated and I'm really not surprised it's leaking. Looks like it's leaking @ the diverter. These large taps normally just unscrew at the joints but I honestly wouldn't bother, you'll be lucky if you'll be able to find out the maker to get parts for it. That and TBH it isn't regs compliant anyway, given that handset will easily reach into the bath.