Just returned from westbound transatlantic crossing on Q.M.2.We had a balcony stateroom (cabin)on deck 8 port side stern (rear) No.1112 at the end of the row of lifeboats,so no restricted view. Port side westbound means you get benefit of any sunshine and we sat out on a number of occasions, would recommend balcony stateroom,worth extra cost.
I have previously travelled on QM2 in a B3 Sheltered Balcony Stateroom. I believe that the B6 grade that you booked is also a sheltered balcony grade, as well as having the obstructed view. The only ones that are true glass fronted balconies are those of A grade and above.
I think if you check it out further you will find that you are now getting a better deal. Also, in most cases, as you have booked a cabin on a guaranteed basis it is likely to be very difficult to get moved as they have upgraded you and that's the way the guarantees work, basically they can put you anywhere on the ship of equal or better grade to what you paid for.
I hope I am not late in answering...I have travelled on both categories. Obstructed view cabins (B5, B6) are virtually Deluxe Balcony Cabins (A- category) with a restricted view because of a lifeboat outside. The overall dimensions, internal layout and decor are absolutely the same with the sheltered cabins.
The only differences are as follows. The sheltered cabins have steel railing, so you have to stand to have a view - if you sit either at the balcony or inside your cabin you see only the sky. While view is certainly restricted in the obstructed cabins, they have plexiglass railing and there are many of them between two lifeboats, allowing for an acceptable degree of sea view.
Second, the entire wall to the balcony in obstructed cabins is from glass, while sheltered cabins have only a twofold door. Add it to the plexiglas railing, and obstructed cabins allow for more light and brightness than sheltered ones. There are people that prefer obstructed cabins only for this aspect of theirs...
Third, the balconies of sheltered cabins are bigger (wider) than those of the obstructed ones. The latter are 248 sq ft large, as are the Deluxe A- cabins, while the sheltered ones are 265 sq ft, the differences being only due to the balcony size.
You should note that boats are far from the balcony in the obstructed cabins, allowing much light and air. But be ready to draw the drapes, as the crew sometimes is working on the lifeboats just outside your balcony...Also, bear in mind that sheltered cabins offer unparalleled privacy and nice protection from the winds, especially on a transatlantic crossing.
And if you had one of the two forward B6 cabins, they allow much unrestricted view, as they are restricted less than half by a lifeboat. They are just great, and I especially booked one of them for my next cruise, and when offered, I declined a free upgrade to a sheltered cabin.