No doubt many people here already know this, but I thought I'd post it for anyone who may not and may have also encountered the problems I have.
I decided to trial the Nik plugins from DXO. In the past I've used Silver Efex, but I hadn't been able to try more of them until I got 64 bit Windows. I installed the plugins for Photoshop Elements, but HDR Efex doesn't work with that program's 8 bit limitations, though the other plugins do. So I installed the suite to Affinity Photo too. Unfortunately Affinity has a major and ongoing problem with Nik. Not only does Affinity have a seriously bizarre colour issue with Viveza (correct colour only displays at greater than 33% magnification), but it can't be used with HDR Efex, despite its 16 bit capability (or it can, but only for a single file pseudo HDR look). Also, if one crops an image and then applies, for example, Silver Efex, the full size image appears in Nik, not the crop (size is incorrect only during the edit, the correct size is saved).
I was very pleased therefore to find a very clear and easy solution on the web (from Robin Whalley) of how to simply create shortcuts to each of the Nik programs, onto which an image file can then be dropped to open it (or more files in the case of HDR Efex, which worked fine).
I had seriously wondered whether to bother with Nik after encountering the above issues, but am now happy. Of course these problems won't occur for most users, but for anyone who has found that Nik was seriously compromised with Affinity and not fully functional with PSE, this is a reasonably easy workaround, as long as you make sure to work with file copies.
Julian