Alright, so I'm back from London. Here are my findings:
I was using Giffgaff as my operator (they run on O2). They have 4g on the 800 MHz spectrum. They also joined late to the 4G party (EE has the inherent advantage in terms of spectrum and speed, and coverage).
In London, 2g service is great - as far as voice calls are concerned. Data on 2g was a mixed bag, depending on where you were. Sometimes it would be as good as Mobilink's 2G, and sometimes, it would be as "good" as Zong's 2g...
3g: the UK has a really widespread 3G service in most cases. There are places where it just craps out. This includes the country side (if you're going to travel by train to another city, prepare yourself for outages*) and underground stations (understandably). 3g speeds weren't too high, but weren't all that bad either - you could average around 2 to 3 Mbps in central London.
But 4g?
Okay. So in the hotel I was staying at (Holborn/Tottenham Court Road, for those curious), I managed to get a peak speed of 10Mbps on 4g. Yes. Peak. In one other place did I manage to get around 11. I don't know if they capped it for prepaid plans (like Giffgaff) or not, but the average 4g speed is lower there. In other places, it would only give me 3 Mbps on 4g.
Don't care about uploads, because I didn't go to England to torrent.
4g coverage was rather shoddy - even with their low frequency spectrum. The coverage wasn't everywhere, to be honest - and it wasn't full signals in all places either. The phone would revert to 3g half the time, which still worked, but obviously not super fast. In the countryside, forget about 4g, unless you're near a town. Inside buildings, it's your luck. Some buildings have better signals than the others (Heathrow airport, for instance).
But what I'm trying to say is that while WIRED services there are much faster than Pakistan in terms of speed and latency (for example, EE, who give 17Mbps standard on the phone lines, and they have GOOD performance, even though EE/BT have problems like PTCL when it comes to setting up DSL connections, because my friend has been waiting for 3 weeks and he doesn't have fiber in his area... And he lives in central London! But I digress), WIRELESS services in London are crap. I honestly respect the operators here (except Telenor, who can't maintain their 3G network and signals) because they tend to be more speedy and reliable, and much faster (despite the higher latency), and with much better coverage overall.
You'd be surprised how London has such terrible phone coverage and internet service, given that it's a big city.
* I don't know if O2 restricts their network to other providers such as Giffgaff, because I saw that my phone was able to "detect" O2 masts, but not connect to them at several instances. But that still is no excuse for not-so-great phone signals and internet services there. Trust me, we have more reliable 3g internet here in Pakistan than they do. It's fine for basic things, but if you want to surf the web there, it's your luck.
Honestly!
I have Zong. At least I don't have signal issues in most places. You guys have Mobilink's. Everyone knows Mobilink's is decent as well. Those who have EE there have the best coverage (because T Mobile + Orange), whilst Vodafone is probably next in line (I don't know, I've heard). O2 advertises as having the best coverage countrywide, but after staying in London, I'm not sure that's true. Others who had O2 in London said similar things.
Interestingly, Manchester and Edinburgh didn't have signal issues unlike London. The internet speeds there were better too!
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