For UVOT spectral files, the canned response matrices are available in the CALDB. They can either be copied to the working directory, or used directly in situ. These are named swu<filter>_dateversion.rsp, where dateversion will be something like 20041120v104. Run
uvot2pha, adding the extension number to the input filename.
>uvot2pha Input (img or evt) filename : sw00374210000uuu_sk.img.gz+1 Source region file name : Usource.reg Background region file name : Uback.reg Output source PHA filename : Usource.pha Output background PHA filename : Uback.pha Response file name : CALDB
Note that the EBOUNDS extension of the response matrices may need the numbers swapping over (to be lowest energy first) - this is necessary for use in ISIS but not for use in XSPEC.
Also, because the bandpasses of some of the filters overlap in energy/wavelength space, so, too, will the spectral points.