It seems that some vendors have hiked up the pre-order price of Windows 7. I’ve seen Windows 7 Home Premium selling for nearly £75 and Windows 7 Professional for nearly £150.
Sadly eBuyer have sold out of their stock of Windows 7, however they do have some good information about migrating to Windows 7, well worth a look-see. [eBuyer update 18.07.2009 – Windows 7 Home Premium is priced at £50, Windows 7 Professional is £89.99.]
If you have pre-ordered Windows 7 at the higher prices, I would suggest ordering via other stores then cancelling your original order. Wait until you are confident that your new vendor can deliver before cancelling your original order.
Other vendors are available, your mileage may vary, etc.