Hi to all interested.
If you wish to use SDRSharp with the SDRPlay rsp1a etc... you will require the extio dll for it to recognise your dongle. This file is available on the SDRPLAY web site.
It will only work with the early version of SDRSharp as far as I know, I use SDRSharp 1316 with no issues.
It is self installing into the sharp directory.