Quoted:
The gunsmith suggested from my initial specification that what i really wanted was a "posers" gun, aka hollywood version?
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I hate to agree with him, but, really, he's right. A carry-handle-mounted scope has a number of serious problems, and no serious shooter would CHOOSE this configuration because of those problems. And you have no need to do so, because your upper is already a flattop.
Another problem you'll have is that the channel on a detachble carry handle isn't the same as on a fixed carry handle upper, so none of the carry handle mounts will fit very well, and you're scope is going to move around (that's already a problem with carry-handle-mounted scopes, but will be worse with a detachable carry handle).
Of course, I also believe that you should be able to configure your rifle any way you want to (and can afford to). It's the American way! [;)] But, I think in the long run that you'd be disappointed, and will probably end up spending more money to mount the scope on the flattop. I'm just trying to save you the money and aggrivation, but again, the choice is yours.
I'm just happy that you're shooting an AR in the UK. Even with the manual-cycling restrictions, it's still got to cause some wet pants amongst the anti-gunners over there! [:D]
-Troy