Just used best buy's price promise to get them to price match a 45W magsafe charger. Now at first i was not aware i could get best buy to price match anything online, when i learnt that this was possible i found the cheapest 45W magsafe i could. http://www.studentcomputers.co.uk
have the 45W version for £20.41, so i asked at best buy and they matched it great deal in my opinion but only available while student computers have stock so be quick :)
In summary best buy now price match online great for any user of this site.
AND you can get a 45W charger for a macbook for £18 how can you say no.