In 2012 both paper 1 and paper 2 of British History, were quite easy and expected.
Its a good subject to choose as British history is quite interesting. It gets a bit lengthy at times especially if you delve into details and contexts but its not boring at all. I am not sure about scoring trend though.
The books to read are as follows

1.British History by Southgate ( Volume 2) (Paper 1 & 2)
This book is a great concise introduction in simple language to building concepts, events, personalities, wars and pacts. The democratic development and agrarian/industrial revolution part is quite nicely written.

2- England Since 1688 By V.D Mahajan (Paper 1)
This books is more advanced reading and needs a background information and contexts of british history. French Revolution and Napoleanic wars, Union with Ireland, William Pitt and American Independence are explained with details, quotations and perspectives.

3.Mastering B. History by Norman Lowe (Paper 2)
Abook which is essential to read for Paper II. Its quite lengthy but easy to read and understand. I feel it is a textbook for Paper II

4.British History by P.C Thomas (Paper 1)
A very good book for making to-the-point notes for Paper 1. Its like a textbook for Paper I.

One can write a lot in history papers so I made bullet points and practiced writing answers with a watch in hand. If you have a fast and speedy handwriting and can form different perspectives to historical events, personalities, wars and pacts with arguments and logic and also if you are a secular/liberal than British History is definitely the subject for you.