There's quite a lot of UK history!
I'll second Choc's recommendation of searching on Amazon - they have a children's section and have reference books there.
For a 9 year old boy, he may find the 'Horrible Histories' series appropriate - they have books which cover periods of UK history. There are also more traditional history books - there's a wealth of school books out there that would be appropriate for his age.
Here's a link to the book on the Victorians:
http://www.amazon.com/Villainous-Victorians-Horrible-Histories-Terry/dp/1407104314/ref=pd_sim_b_27Whilst not UK history, you may also be interested to look at the 'ology' series - my children have the 'Egyptology' book - very good:
http://www.amazon.com/Egyptology-Search-Osiris-Emily-Sands/dp/0763626384