Small budget effective computer - Big Data

[Karta]

Hello,
I would like to ask for advice when choosing a laptop. I need to change my old laptop for another one and I have some requirements. I would like it to be a convertible laptop. I often travel, so it must be light and not so big (14 inches?). I often works on a large amount of data and must be relatively efficient and fast. With additional advantages, it's great if it had a backlit keyboard and long time work on battery.
The price can not exceed 600 pounds, but I will consider the suggestions altogether.
I am waiting for a response, thx.

 

[Karta]

Thanks for answer
In that case, it's possible that I'll have to go a bit higher with the price if I want a high-performance computer.
I have to think about it.
Thx