@Martyn:

The fact is that printing and distribution is a small proportion of printed book costs. About 10-15 per cent on average. And ebooks attract VAT (UK sales tax, at 20 percent). Printed books are VAT-free. So there's no reason, if you base your argument on production costs and tax, why ebooks should be cheaper in the UK than printed books.

Sources:
(1) http://www.nytimes.com/2009/05/17/weekinreview/17rich.html -- says that combined printing and distribution costs of print books account for 12.5 per cent of the average hardcover retail price.
(2) Sunday Times (London), 6/2/11: They quote a member of research firm Enders Analysis: 'The cost to manufacture a paperback is less than £1 including transportation. The real costs are the advances to authors, the editors, and the marketing budgets.'
(3) http://theharperstudio.com/2009/02/why-e-books-cost-money-to-publish/