I just had a really productive chat with John Lewis about the GT50, dirty screen effect, and possible solutions.
I have three options.
1. They will send me another replacement GT50, in the hope the third will be better than the last two.
2. They will allow me to wait until 2013 models are available. At this point I can exchange the GT50 for a GT60 (obviously paying the difference in price).
3. A combination of the two options. I can get a replacement GT50, with the option of upgrading to a GT60 once available.
My initial thoughts are that I lose nothing by going for option three. The worst that can happen is that the third GT50 has exactly the same problems, at which point I can go for option two. However, replacing the GT50 again is hassle all round and I've little confidence the third set will be any better.
I'd welcome any thoughts on the above.
I'd also like to commend John Lewis once more for exemplary customer service.