Performance at A-Level mathematics is a better predictor of CS success than performance at A-Level Computing (which does involve programming), hence it's unlikely that universities will make it a requirement.
I see it as a failing of A-Level Computing more than anything. But I found about half the of first year was wasted on me, to break this down:
Com 1001 - Software Engineering Crossover Project
UML, requirements, analysis, design etc.
All covered in A-level computing.
Com1002 - Foundations of Computer Science
Maths, not covered at A-level in any subject.
COM1003 - Java Programming
I struggle to remember which concepts were covered in A-level and which I taught myself but sitting through lectures which taught what a variable was, then what classes and an objects are was painful. There were some golden parts that were enlightening but these were few and far between.
COM1004 - Web and Internet Technology:
Cryptography - not taught at A-level.
Ethics, law, piracy - taught at A-level.
COM1005 - Machines and Intelligence:
The first semester of this was writing about AI because we 'didn't know how to program'.
The second semester was learning systems which was very enjoyable and quite complicated.
COM1006 - Devices and Networks:
Anything that was taught at A-Level (boolean logic etc) was extended on and there was little time spent on basic stuff.
If they had made Computing A-level a requirement I'd have gained just shy of 6 months education I reckon (£4500 for future years), and if Computing A-level was extended upon to improve it then they'd be able to teach even more interesting topics. I think the requirement of Mathematics (which was required at my university, but not all) just shows a general aptitude in the appropriate areas, and only had direct relevance to two modules (one during first year and one in second year).
Any course with too many applicants for its spaces (the top Universities) could require Computing A-Level if it became more mainstream and I believe this would increase the standard of education possible.
EDIT:
To bring my point back round the article. This news makes me happy because a move from ICT towards Computing at GCSE would likely increase numbers taking Computing at A-level and definitely increase the quality of the A-Level. The number of people taking it and the quality of teaching at this level would hopefully remove some of the simpler concepts that Universities are having to teach.
The problem with making something like computing (or any non-standard) A level a requirement is that it immediately limits people who couldn't study it. Not all schools offer computing (or other less popular A levels), and by making it a requirement you're penalising those who had to attend them. In practice, that means rural and less-well-funded schools.
There obviously has to be some prerequisites. Perhaps the solution would be a summer school for students without A Level computing. Most universities offer a foundation year for people who want to study engineering or maths related subjects but don't have the A levels required. However, given that you only need to cover under 1 semester of work, you'd be pushed to convince people that because they didn't study a computing A level they have to add an entire year to their degree.
Probably the best option would just be to make it a strongly required subject, and cover the basics in less time. If you don't have computing A level, you need to work harder.
The reason that Maths A-Level is used is that it measures abstract thinking ability which becomes important for more advanced CS.
What my university (Bristol) did is that the introductory units had two variants - one which assumed programming experience and one which assumed none, that way students could self-select based upon experience which is probably a better solution.
Most degrees actually have a period where they're bringing everyone up to the same level (be it Physics, Psychology or Economics) because there's a lot of variation in school level teaching and that's always going to be there unless the government starts micromanaging every school lesson.
Com 1001 - Software Engineering Crossover Project UML, requirements, analysis, design etc. All covered in A-level computing.
Com1002 - Foundations of Computer Science Maths, not covered at A-level in any subject.
COM1003 - Java Programming I struggle to remember which concepts were covered in A-level and which I taught myself but sitting through lectures which taught what a variable was, then what classes and an objects are was painful. There were some golden parts that were enlightening but these were few and far between.
COM1004 - Web and Internet Technology: Cryptography - not taught at A-level. Ethics, law, piracy - taught at A-level.
COM1005 - Machines and Intelligence: The first semester of this was writing about AI because we 'didn't know how to program'. The second semester was learning systems which was very enjoyable and quite complicated.
COM1006 - Devices and Networks: Anything that was taught at A-Level (boolean logic etc) was extended on and there was little time spent on basic stuff.
If they had made Computing A-level a requirement I'd have gained just shy of 6 months education I reckon (£4500 for future years), and if Computing A-level was extended upon to improve it then they'd be able to teach even more interesting topics. I think the requirement of Mathematics (which was required at my university, but not all) just shows a general aptitude in the appropriate areas, and only had direct relevance to two modules (one during first year and one in second year).
Any course with too many applicants for its spaces (the top Universities) could require Computing A-Level if it became more mainstream and I believe this would increase the standard of education possible.
EDIT: To bring my point back round the article. This news makes me happy because a move from ICT towards Computing at GCSE would likely increase numbers taking Computing at A-level and definitely increase the quality of the A-Level. The number of people taking it and the quality of teaching at this level would hopefully remove some of the simpler concepts that Universities are having to teach.