I suggested O. stricta because of the spines but I have looked at the O. ficus-indica on Scrivener Hill Opuntia ficus-indica (Indian Fig, Spineless Cactus) on 20 Nov 2015 and those plants also have similar spines. Should I change to Opuntia sp.? If I get there when I have a rubbish bag it will be removed anyway.
The Plantnet key separates stricta from ficus-indica on the size of the segments - stricta and another with segments usually less than 30 cm long, ficus-indica with segments usually more than 30 cm long. The measurements they give are: stricta mostly less than 20 cm long , ficu-indica 30-50 cm long.