I though I would share my experience, should it be of use to anyone else;
After a surreal amount of review reading I decided to plump for the Dell U3415W which is a WQHD 34" panel @ 3440x1440, this model has largely been replaced by the apparently not so good U3417W. The few places that still have stock of the U3415W are generally charging a premium for it, but a bit of searching finds it at a reasonable price.
The monitor is QHD, the same as the laptop I'm using, but is obviously considerably larger so pixel density isn't as high which was a concern, but in reality isn't a problem & text is more that sharp enough at the distance I'm using the monitor at 2>3 feet. 3440x1440 is absolutely fine with standard Windows scaling, no adjustment being required.
Many of the reviews that I've read suggest that a 34" 21:9 monitor will comfortably allow 3 applications / Windows to be on screen, side by side concurrently, but things start to get uncomfortably narrow at native resolution / no scaling. The monitor is however quite usable with 4 windows open in a 2 x 2 stacked arrangement.
The integrated power supply also keeps thing neat & avoids another power brick to hide / place conveniently
