Avios also does £1=1 avios at Argos, so if your collecting nectar points you can potentially collect 1 nectar, 1 MR, and 1 avios per £1 at Argos, and if needed convert the MR and avios into nectar points. If I’m not missing something there?
And of course you can get avios points at other retailers as well (though mainly online I think)