FWIW, the Humax HDR-FOX was judged the easiest to use (out of a sample of three) Freeview PVRs some time ago by The Gadget Show, and so far as I can make out from comments on the forum that remains the case (at least in the Humax stable). However, any PVR will require some training, so it is not clear to me that the relative ease of use (and available expertise) of a HDR-FOX outweighs that it will be necessary to buy second hand.
Again FWIW, I made life a little easier for my 87-year old "supported user" by adding a Harmony programmable remote so that all the functionality of the TV+PVR combination is dealt with on one handset (eg volume control always breaks through to control the TV without having to select mode). The Harmony has to be set up specifically, and there are only enough buttons for a subset of the functions available (but how often would she need the "VFORMAT" button?). To minimise confusion the TV is only a monitor for the PVR (and never used stand-alone) - but there are occasions when things get out of sync and I have to straighten her out.