Charver will need to set you straight. Their constitution is stronger than you want to believe in this post.
This is the important bit:
The reality is they practice separation of powers, even though you don't want them to and think it's "optional" for some reason. Your example was of a government that practices a different version of separation of powers, but it is certainly practicing that notion. The idea that it must be formed exactly like the US is simply Amerocentric inanity that recognizes nothing at all outside the US.
Ooh, it's not often i get to put my constitutional head on.
This may sound like sitting on the fence here but i think you're both right. You can argue that our Constitution is both "not worth the paper it is not written on" and responsible for producing a stable democratic system and make a convincing argument either way.
There is a separation of powers albeit a weak one in comparison with the definite separations defined in your own constitution. Through the quirks of history we have developed a series of checks and balances to ensure a degree of executive, legislative and judicial independence and flexibility which ensures we do not run into the problems of deadlock which you're all too familiar with over there. On the other hand flexibility leads to uncertainly.
WM is right when pointing out the dominance of Parliament (or more recently the Executive in Parliament). For example, the judiciary, technically, has no power to strike down legislation. When the Human Rights Act was passed, in 1997, incorporating the European Convention on Human Rights into English law it was an opportunity to give judges that power but Parliament insisted on the preservation of the Doctrine of Parliamentary Sovereignty. Therefore the most a judge can do to protect our fundamental human rights is to make a declaration of incompatibility and ask the government to think again, while the offending law remains valid. That'll frighten the buggers, eh?
Are you sure you wanted me to answer this?
Anyway, although i've just said that judges aren't technically allowed to veto legislation, they do. Under the European Communities Act (ECA) we're signed up to the concept of EC law, which takes precedence over domestic law. So UK legislation has been vetoed by judges as being incompatible with EC law. This would be a breach of Parliament's Sovereignty but it is suggested that because Parliament intended EC law to be supreme, by passing the ECA, then the judiciary are merely giving effect to Parliament's will and, moreover, that if Parliament gave a clear intention to act inconsistently with EU law then the courts would be obliged to submit to Parliament's will but this is not definitive. All clear? No, i didn't think so.
We also have the increasing problem of the blurring of Executive and Legislature which has led to what many see as an "elective dictatorship" (thanks for that Lord Hailsham) as party discipline has eroded the concept of MP's independence and the House of Lords has been sidelined. In addition the increased use of enabling legislation which, once passed, allows the executive to make changes to the law without Parliamentary scrutiny can be viewed as the encroachment of executive into the territory of the legislature.
So, how strong are the separations? Christ knows. As strong as the Executive in Parliament is willing to maintain them, i suppose, but that would be dependent, ultimately, on the willingness of public opinion to accept it.
In truth i could write a 10,000 word essay on this and struggle to give a definitive answer. This is how dull i can get when i'm not being daft.