Unless you are going to be carrying your laptop outside the house often go for the largest screen you can find. That will give you the biggest keyboard for comfort on the hands as well as the eyes.
This sort of machine will not have a huge battery life but not a problem if you are using it at home.
Unless you are hardcore gamer playing the latest high spec games or a video editor you do not need a high spec machine.
It should have 4GB RAM.
Minimum 500GB hard drive. If you store a lot of movies you will need more.
I like this one:
Amazon.co.uk User Recommendation
But really you will get a lot more for your money in a desktop. Unless you absolutely need a laptop, buy a desktop. You could buy a decent tablet for web browsing etc in your armchair, in bed or in the garden with the savings.