Very easy: download the app from the Google Play store and open an account. It's free, but you can pay for additional services (the basic plan has everything you'd need). Then you can open an account in any currency you want (GBP, Euro and USD make sense) and then you can transfer in money using a debit card and convert currencies at any time. They do use a worst exchange rate during week ends, but during work days it's one of the best rate you can find.
I can send you a referral link, but I don't think this currently would give you any advantage, there is no promotion at the moment.