Seems a good deal to me, typically extended warranty for 2 years with d&g would cost around £80 depending on product etc
What the Bosch website says
We're celebrating our 75th year in refrigeration by giving you 2 years extra on your guarantee - FREE.
From September 1st to December 31st 2008 To celebrate our 75th year of producing excellent refrigeration products we are giving you the chance to claim up to a total of 4 years warranty. Buy any Bosch frost free fridge freezer (see qualifying list below) between September 1st 2008 and December 31st 2008 and you can claim an extra 2 years call out, parts and labour guarantee absolutely FREE.
You can also get this deal through major high street chains, ie john lewis etc