Decided it's time for a change of phone and I'm looking for a smartphone.

I'll be using it primarily for texting, apps and internet browsing, with just the odd phone call and music playing.
A fairly large screen is necessary to browse the internet
A QWERTY keyboard would be good - not necessarily a physical slide out one, but at least one on the screen

I'd rather pay a large lump sum at the beginning and a smaller amount monthly if possible (ie - £300 up front and £15pm rather than a free phone and £35 pm)

Unlimited (or a lot) of texts and internet is a must


I'm only buying from somewhere reputable and yes, I'm in Britain as highlighted by the £££

Thanks in advance