Yes, I'm from the UK too but the idea of 'modesty' varies culturally - like you said, people here seem to find no issue in showing a lot of their legs (I haven't been to Japan yet, so I don't know about there, but here I see lots of girls wearing long hoodies & (what looks like) nothing underneath) - but for my cultural upbringing (Pakistani), I prefer to cover that part too, lol
Anyway, all that to say do what works for you. My outfit formula for 'comfy colourful covered chic' (that's my style moniker on this forum) has become cotton, boatneck, long or 3/4 sleeved tops, tucked into loose maxi skirts or bottoms that taper for practicality's sake (cargo pants/ ankle cuffed trousers). You might prefer shorts instead - try Uniqlo, Muji or GU? (those are Japanese brands we have here in HK that I know do good, machine washable basics)