First up: oil. Halfords think that a MiTo takes SAE 0W30, but that's wrong. The correct grade according to the manual is SAE 5W40 ACEA C3 (the SAE 5W40 refers to the viscosity, and the ACEA C3 is a general oil type code). While anything meeting that ought to be fine, there's an additional Fiat specification as well - 9.55535-S2 - and very little lists that. One that does meet all the specifications (and in fact is what the garage used) is Castrol Edge "Turbo Diesel", which I find amusing given that my car is neither turbocharged nor diesel.
Second up: spare bulb kit. Again, Halfords is made of fail, both because they've decided to ignore the standard bulb classification system and make up their own, and once I decoded that I found what they list for a MiTo is also wrong. Epically so, like having entirely the wrong headlamp bulb and suggesting indicators that are not orange-coloured. None of their bulb kits have more than a couple of correct bulbs in them so here I'm best off springing for the official Alfa kit.
Third up: screenwash concentrate. Or not, as the concentrates are scented and only the ready-mixed is plain. I don't think I want berry scented screenwash...
Some point in the future: replacement wiper blades. The internets seem to converge on 6 months as the lifetime of a set of wiper blades so I'll keep an eye on them for now. And when it comes to replace them, I'll probably take the existing set into Halfords to compare with what they've got. The front blades are not just a plain strip of rubber, but have some fancy fixing mechanism, and the rear blade is actually part of the wiper arm assembly.