That's true but the key word is "
interests". While it was probably in the British interests to avoid a major war in Europe it could do little to influence the events directly because this would be pretty much a land-locked conflict. In OTL when Germany was (at least in theory) considering a new war against France in the mid 1870's, the Brits influenced Alexander II and his Chancellor, Gorchakov, to exert some pressure upon Berlin on the French behalf (which resulted in the beginning of the cooling of the German-Russian relations). So, at least to some degree, situation depended on a confused nincompoop (Alexander II) and the head of the Russian diplomacy suffering from the age-related mental problems (a complicated combination of the obsession with the "European Concert", memory loss and Grandiose delusions about his own importance). Objectively, interests of the Russian Empire in such a war had been nonexistent: French Republic was neither an ally nor (yet) a source of the major investments into the Russian economy while, OTOH, as a "compensation", Bismark was ready to offer Russia free hand in the potential war against the Ottomans (in OTL war of 1877 - 78; not that Russia really needed it by any stretch of imagination), which in practical terms would mean keeping A-H out of the picture and support construction of the Russian Black Sea Fleet (even if the treaty of Paris was officially denounced by Russia in 1871 Gorchakov was resisting the restoration of the Black Sea Fleet not to offend the Brits).
So, if we assume that the war really happens (whatever the outcome) while Russia is unambiguously neutral (or rather neutral-friendly to Germany), then the Brits could do little besides sailing somewhere off the French and/or German shores and making the diplomatic noises which could be easily ignored. Russian position would probably prevent A-H from interfering and you have 1:1 scenario (of course, this is a highly simplified schema

).