For Hongkongers arriving in the UK, there are many good networks to choose from, including Vodafone & EE, but I recommend O2 for one very good reason. As well as having excellent network coverage, they have :

O2 Priority

Why a picture of pizza?

For £8 a month, you can get four Greggs sausage rolls, four cups of coffee, four free tickets to the Odeon cinema, eight cocktails and a free buffet lunch at Pizza Hut. There’s even more, but I don’t have room here to list everything.

If you plan actually to use it as a phone, you also get unlimited calls and 30GB of data!