I stopped in to Harrod's today and it seems they have huge sales on some of the pens in their writing department. Their remaining stock of Pelikans is quite small, but I believe there is an M800 (new style logo, black/black) for about 199 pounds, a Fire LE, some Majestys and a number of rollerballs discounted 50%. If you're a visitor, you can also get VAT back, which means another 8-12% off. Edelstein ink is 9 pounds for those interested.
There are some good deals on other pens as well, as well as a silent sale on Pilot-Namiki