Just bring GBP with you. You can exchange it here easily and prob better rates too.
As for the banks, tell them you are going overseas and you need to unlock the card. This way you can use it in China without hounding NSA or some shit.
Carrying all that cash is dumb, just carry a few thousand RMB and rest in GBP. Enough to get you off your feet.
You can open a bank account in China easily, but what is your goal, do you want to send cash from China to UK? Or just someplace to house your money, then any bank should suffice. There are other ways to send money overseas, linking one account is difficult. HSBC is able to do it, but you need lots of money in order to do so. I had a friend in HK who was able to do this… He had upwards of over 1million HKD in his account, so he had special treatment.