Another thing that isn’t always obvious, but in public transport try to avoid having loud conversations (especially on the phone) or watching videos/music out loud. A lot of non-Brits do this on my daily commute and it’s very irritating to everyone. The problem is that Brits are kind of passive and avoid confrontation, so even though everyone is silently suffering they’ll probably never actually tell someone that it’s annoying or ask them to be quiet. So that person probably won’t know.

But yeah - use headphones and treat public transport (especially trains!!) as a quiet space. Buses can vary a lot more. If in doubt, try to fit in. Avoid adding volume to a space, and copy what the Brits seem to be doing. The general goal when in public is to be as unobtrusive and un-annoying as possible. Aka stay out of people’s way, stay quiet, queue respectfully, avoid touching people or intruding on their personal space as much as humanly possible, don’t stare at people, don’t push/crowd people, don’t eat anything too strong smelling, etc. Sounds like a long and intimidating list but it makes sense once you start to follow it. And, as I said, you probably won’t face any consequences for not doing these things - nobody’s going to confront you - but most people there will be very internally annoyed.

Final thing that’s a bit different, people are friendly and if you’re stuck you’re always welcome to ask for directions etc. However, don’t be surprised if people are suspicious or in a rush and refuse to stop (often you really do have to run to catch the next bus or train).

Also, try not to treat people too differently. There is a massive South Asian diaspora in the UK and millions of British people of desi descent who are, at this point, more culturally different -and British - than a lot of native South Asians realise. They also come from all over and tend to mix into a more fluid cultural identity here. Pakistani/Indian nationalism and politics don’t really carry over or hold much relevance for young 3rd/4th generation Brits.

Point being, don’t assume that because someone is brown they are Indian or that you will have a lot in common. You can usually tell by appearance whether someone is British born or a recent immigrant (the British desis often have paler (sun deprived and anaemic!) skin, different hair/makeup/clothing styles, different perfume/deodorant preferences, slightly taller height, etc). Sometimes you can’t. Chances are they will still have lots in common with you. But they might not understand hindi, and there’s a large chance they won’t speak it. They won’t necessarily be friendlier to you than white Brits, and their politeness might come across as distant but really it’s just a cultural difference and they’re just as unlikely to act with immediate familiarity and openness to strangers as any other British person on public transport. They might get annoyed if they think they are being treated differently because of their skin colour. I think these kinds of things can be a bit of a surprise/disappointment to Indians who visit, but you have to remember that many desi communities were established not long after partition - it’s been decades and generations since then, the cultures have diverged and India has changed a lot since those first families left.