What do guys wear on the first day? [United Kingdom]

I did my undergrad through the Open Uni - I have never attended an on campus lecture in my life so I dont really know what a first day PhD student should wear.

I know that after the first few days/weeks it will end up being jeans, trainers and a t-shirt, but meeting supervisors and cohort for the first time I am guessing something more smart-casual? Are chinos, polo shirt and brown shows about right? Is a smart hoodie too casual?

Male, STEM, UK