They probably knew this when they stopped you. MOT, tax and insurance are all on databases and some police forces now have number plate recognition systems that mean that if you drive around like this you're going to get pulled.
You don't really have much option other than to 'fess up.
Is it less than 2 years or more than 2 years?
If it's less than 2 years you're on probabtion and if you get 6 or more points in that time you'll go back to being a learner.
Driving without insurance is 6-8 points
No points for lack of MOT
Pretty sure it's no points for the car tax too
So if it's less than 2 years - congratutations you're a learner!
http://www.2pass.co.uk/retest.htm