I can point you in the direction of many clinical colleagues who will identify the lack of support services, such as no MRI or CT at weekends, or no histopathology cover to aid in renal pathology diagnoses, or no immunology cover to help determine rare heritable disorders. Some of their comments are not justified by clinical need or by economics - not sure it makes sense to have weekend working for histopathology myself - but certainly the imaging availability is an issue at virtually all District Generals right now.
Fortunately the technology has caught up a bit, and now automation, new testing protocols and computerisation etc all allow for a 24/7 service for pathology and there is no real reason that MRI/CT scans should not be available 24/7 either where necessary.
The reasons why the mortality rate is higher at weekends has been documented and is multi-factorial in nature, although I think most studies seem to concur that lack of senior clinical staff at weekends is the most important issue.
Fact is, many aspects of healthcare within the NHS and indeed outside of the NHS run on a 5 day week, when it should be considered as being a 24/7 service