They have had a global sale for non agency books going on for a while now (40% off newish books and 60% off backlist books). Still 40ish% off on the Uk site, as it follows the US for deals by a day or 2 it looks like it's time for a quick splurge
Edit
Sorry, it looks like you are using the UK site - deals seem to be back on now (May have been a temporary glitch as they changed the deal to a slightly different one).