It turns out that Coop tinned chickpeas are tinned only with water, whereas the chickpeas sold by the local Nisa garage* which advertise themselves boldly as 'France's favorite vegetables' are tinned with slightly salty water. This makes all the difference to the eventual hummus. The chickpeas tinned in plain water *definitely* need added salt, and the lack of salt in the mix somehow causes the garlic to become unbridled and gallop all over the place shouting 'I AM GARLIC! HEAR ME ROAR!' The ones tinned in salty water don't need any more salt (or to my taste they don't, anyway).
Hummus is very tasty with tahini made straight from sesame seeds rather than pre-made. I suspect the reason most recipes say 'tahini' rather than 'sesame seeds' is that when you toast the little sods in a little oil they develop a passionate desire to stick to everything, rivalled only by polystyrene beanbag beans. Which is fine if you don't mind licking sesame seeds off your pans (and I don't) but would probably really annoy some people.
*what a treasure trove that place is, the kind of small shop where you can buy road salt, lemons, dog toys, chickpeas, beer, bacon AND deeny boppers.