One of my favourite postwar buildings is Frederick Gibberd's Liverpool Metropolitan Cathedral, or Paddy's Wigwam.
The circular crown design, its spectactular wrap around stained glass and the dramatic realisation of the form with its diagonal buttresses makes an instant impact, and it's as beautiful inside as it is outside. It's a much more extravagant design than is usual with Gibberd, who while adding decorative touches in his more typical buildings, is also usually rather restrained.