I have lived in Milan for most of my adult life and I can tell you there are plenty of badly dressed people around! I don't mix with any British people really, all my friends are Italian, but even after all these years, I am still the stand out Brit, despite dressing like them. The main difference is size, I'm just bigger and made differently. I have thin mousey, wavy hair, I'm stockier & they all small framed and have thick dark shiny locks too.
None of my Italian female friends work out but none of them are overweight either, but they all drink much more than me (beer, prosecco) but they do eat differently, lots of salad just with olive oil & vinegar, grilled meat, grilled fish, veg & fruit, zero dairy. None of them have a sweet tooth either whereas I do. It's also perfectly acceptable here to say someone is fat, the Dr will tell you too. Everyone discusses their weight, the state of their livers, and cholesterol levels around the dinner table!
I would say most of my friends dress in simple non patterned classics, usually good quality clothes, but not that cost a fortune too and certainly not designer, the majority own very few clothes actually, clothes cost and Italians generally are not well paid, but don't buy cheap throwaway clothes either ( although in recent years Primark has opened here.) They never go out in clothes that are not clean or ironed and they are usually made of natural fibres.
On a recent holiday I noticed how easy it was to spot British female tourists, my Italian friends loved their style actually, a few described them as brave and why? because they were individually! Polka dot, flowery or 'loud' bikinis some with high waists, floppy hats, long dresses in the evenings (long dresses are defo a UK thing, i've never seen an Italian woman in a long dress with white trainers). My Italian girlfriends were all in the same black string bikinis, simple earrings and a simple necklace, they don't wear cheap costume jewelry but something inherited or given as a gift. Footwear is usually flat leather sandals such as Birkenstocks. They all dress in a very similar way and yes the puffer jackets & scarves come out as soon as the temp drops to what would be a hot day in the UK. It's all about being seen to dress appropriately and not necessarily individually. One day this summer I wore knee length bermuda shorts, with birkenstocks and a simple white t-shirt and I was told I look like a 'stereotype German tourist' apparently, I'm sure though and olive skinned Italian would have looked a lot less German
Regarding the heat, you just get used to it, today's 29° and I'm not overly hot! When I go to UK in the summer months, everyone is in summer clothes and I am freezing in a jumper and coat usually, so works both ways!