brother British history is a scoring subject no doubt but for a good score you should have good understanding. the paper 1 of British history is very easy and can be covered in short time if you have a good cramming quality but for paper 2 you will have to have in-depth study as it is lengthy and time consuming. it is very interesting, but also little lengthy. you will have to cram dates, names, wars and treaties ....
i will recommend you following books

paper 1

southgate's book volume 1 last portion for james2 till end
southgate's book volume 2 till battle of Waterloo
Norman Lowe book initial chapters till date 1850

for paper 2
Norman Lowe from 1850 till Margaret theater
also study southgate's book volume two ...

rest think twice b4 you opt any subject because it is you who have to study brother.... best of luck ...