According to 
this recent article, the waiting time for a non-emergency CT scan in Great Britain is 
5 weeks, and for an MRI is 
14 weeks.  These numbers are considered huge improvements from the truly awful state back in 2001, when the waiting times were 7 weeks and 21 weeks, respectively.  Also,
...[T]wo out of three doctors and nurses said they often did not get results when needed, and a half said the delays affected patient decisions daily.
In contrast, here in Denver, the waiting time for both is generally less than 24 hours.