We last ate there in December and we were there during Wishes, but we didn't have a seat at the window facing MK. We were able to go out onto the viewing platform, but there was a problem with the music - for a while we had nothing at all and then we were treated to the Thomson Twins!
Only those dining there are now allowed to enter the restaurant - you have to check-in on the 2nd floor - which means there is far less of a scrum during Wishes.
In my experience, it's quite tricky to time your PS for Wishes, but maybe I'm just not tenacious enough. For a start, for your own peace of mind, you will probably want to make your PS before the Wishes times are announced, so you have to guess based on last year's timings. Invariably they turn out to be different, so you have to phone back and change the time of your PS. Often the timings will change again, so you have to keep an eye on them, right up to a few days beforehand. Whenever I've arrived, the window tables facing MK have, unsurprisingly, always been taken. You can tell the check-in clerk that you are willing to wait for a table, but bear in mind that anyone already at a table is unlikely to leave before Wishes has finished. I know I wouldn't!
Edited to say that, if you ate at the Concourse Steakhouse, there is a viewing platform on the same level, but you would have to leave the restaurant - not something I'd want to do. I don't think you get to hear the music from that position, either, and it's really not the same without it.
It was wonderful.
