The four men had planned to remotely detonate a car filled with explosives at a military facility used by volunteer forces in the town of Luton, 30 miles north of London, The Daily Telegraph reported.
The head of the terror cell, Zahid Iqbal, 31, and his lieutenant, Mohammed Sharfaraz, 25, were sentenced to 16 years and three months. In pronouncing their punishment, the judge said the men posed a significant danger to the public.
Umar Arshad, 24, was sentenced to six years and nine months in prison, while Syed Farhan Hussain, 22, was jailed for five years and three months.
All of the men had previously pleaded guilty.
In earlier testimony, the court heard that Iqbal and one of the other men discussed attacking "multiple targets," including the offices of MI5, an agency roughly the British equivalent of the FBI.