US readers may not know it, but Amazon isn't exactly flavour of the month in the UK at the moment, as it turns out that they feel that multi-national companies shouldn't pay tax like the rest of us. There is talk of a boycott.
There's no doubt that Amazon is a great deal from the customer's point of view. Most places selling my books will charge you more than Amazon. The Book Depository often offers better prices, but they are owned by Amazon as well.
UK purchasers will find e-book versions of The White Rajah and Cawnpore cheaper on Google Books. This is useful if you're trying to save money, but not a lot of help as a political protest because Google has been known to dodge the odd tax bill as well.
Of course, you can always buy either of my books through an old-fashioned bookshop. People in London could try Foyles, who may have it in stock. Branches of Waterstones should have it on their system, so they should be able to order it easily. Other booksellers should also be able to order it in for you. Bookshops do still serve an important role in publicising books and getting people to read and they do seem to pay their taxes.