How much do you want to spend? Are you happy with a Dell refurb? There are about a gazillion options so it’s hard to focus on one. Battery life is really the only thing you’re specific about & this is almost impossible to gauge as the times reported by the manufacturers are about a s reliable as MPGs quoted by car makers.
Eg. new Dell Inspiron 15R does what you need – £430 + delivery
or, Dell Outlet Studio 15 – Tons of power, i7 processor, loads of RAM £514 delivered.
Your apetite for a bargain vs wanting something new & shiny would be one of my first questions, Eg. I just got a an i5 laptop from PCworld’s refurb shop on ebay for £350, a risk but seems to have turned out well so far.