Cheers for the prompt response kevin_intel.
I forgot to point out the incredibly important bit... this is on Windows 7, using the latest Windows 7 HD 5000 driver.
The HD driver supplied by Apple with their Boot Camp drivers showed this problem in Windows 7. I then updated the W7 driver using the Intel HD website to download and install, and still the problem exists.
I suspect the resolution is quite simple - either a software tweak on my side, or within GLEW for windows - but I'm hopeful if the HD driver needs adjusting then a future Windows update won't be out of the question?
I can help provide any diagnostics / testing to resolve the issue - I'm an experienced software engineer and games dev, and I'm used to chasing down issues like this when they occur. It's quite sad to move from the old mac air to a far more powerful graphics solution and see it crippled in this way (I've had to disable normal mapping in my engine for this machine) so I'm very keen to help with a resolution.
If it means waiting on Apple - then it will never happen - I have plenty of experience in dealing with them with major iOS related issues that sadly never get dealt with.
Fingers crossed!