Ethanol is hygroscopic, it attracts water and absorbs moisture from the air causing condensation and leads to corrosion of car parts and damages plastics, bad news for M cars over the long term.
Tesco fuel is handy when you do your shopping then fill up with Momentum but as the fuel tester says watch this test if you value your M5 engine.
My tip is to use Texaco Supreme + 99 with Redex petrol additive to protect the fuel system and injectors.