This looks like a bit of a glitch on the Halfords website. It looks like they have this widely available at a sale price of £79. To get it for £45, follow the link and scroll down until you see this item. Do not click on the item to view details as it takes you to an error page. Just click on "Reserve or Buy" to add it straight in to your basket. Job done.
Price edited to show 10% discount for today. Thanks Chanchi32.
Direct link now available, thanks Darzen.http://www.halfords.com/sat-nav-audio/sat-nav/car-sat-nav/tomtom-start-25-5-sat-nav-uk-roi