I've heard that regular petrol (92 octane ULP) from some fuel companies is not good for motorbikes as it is intended for cars only. Is this just an old wives tale?
Very untrue. Both car and motorcycle engines are designed for gasoline, and just like cars, using higher-than-specified octane gasoline provides no advantages (unless you're advancing the timing or other modifications, in which case you'll tune for a certain minimum octane).
High compression or forced induction designs (turbos and superchargers) in both cars and motorcycles will require premium, and will specify as such. Most sport bikes are high compression ratio (some as high as 14:1 or higher), and should only be run on premium. This is the same as cars that require premium - you will have lots of engine problems if you bring a turbocharged engine to full boost on regular octane gas.
So - there's no clear rule like 'motorcycles need premium' or anything of the sort. The manufacturer will specify a minimum octane, don't go below it. Going above doesn't hurt, but doesn't do anything for you either so you're wasting money.
Caveat: if you're a tuner, you should know what you're doing and don't need to ask this on SE. If you suspect you've purchased a car or motorcycle that has been tuned (has a chip, powercommander, or advanced timing) you should ask the previous owner if it has higher octane requirements than stock.