10.1.1 of this is the closest mention you get on Apple site.
http://store.apple.com/Catalog/uk_inst/Images/salespolicies_individual.html
tbh for the £58 I would just buy the full package. I am currently going through hassle of getting support to confirm I have 3 years via HE etc (my 1 year runs out tomorrow).
Reading other places the general consensus is you are covered for 3 years but the warranty check site will only ever show 1 yr phone support against your serial number. If you paid the £58 or bought some other applecare you get an enrollment code which will then make the site reflect your 3 year status.
People recommend this if you are selling on your mac (which technically I think is not allowed under HE conditions) as it showing 3 yrs as opposed to 1 yr means you can charge more for it etc.
To get some independent advice I would search macrumours and apple forums where the question has been asked many times.
rp2000