When attempting to purchase LR6 as a standalone upgrade rather the full version from the UK there are no prices available. See link.
Not everyone wants to sign up to monthly subscriptions for the CC Photography Suite so does anyone know when Adobe UK will release a LR6 Upgrade package?
If you click buy (where the full price is display), it takes you to a sub menu. Select "Upgrade", then the version of Lightroom your upgrading from, the upgrade price will then be displayed (£59.09)