im surprised no one has mentioned this on here yet as its being spoken about in a few other places. There is a public consultation which has been opened up about expempting historic vehicles from going through an MOT. There are 4 options available, the options being - leave as is, exempt pre 1920, exempt pre 1946 or exempt pre 1960
below is a link to the consultation - its worth reading the supporting documentation along with the consultation as they detail how many cars in the UK, how many are pre 1920, '21-'45 and '46-'60 and post '60. They also detail how many have failed an MOT, speak about mileage etc. etc. etc. the consultation is open until January 2012.
Historic Vehicles MoT Exemption Review - Consultations - Department for Transport