Hi there,
I have just graduated with a law degree so I can help break down the process for you:
An undergraduate law degree is 3 years as standard, optionally 4 years if you take a year abroad somewhere. once you have finished your degree there are then several options depending on what you want. To become a barrister you need to study for a further year on the Bar Vocational Course. To become a solicitor you do a further year on the Legal Practice Course. Alternatively, you can opt to study for a further period (Masters Degree, or PHD).
So technically the answer above that said 4 years is correct. 3 years undergraduate + a further year on the BVC or LPC. You then find employment, where you will undergo training for a further period (but you'll be provisionally qualified)
Hope that helps :)
Best of luck with your plans.