Hi Hugh.
Yes, unfortunately the modern Nait 5 series does not have an input for a turntable. They also do not have wobbly front panels! (wobbly sockets, yes, .. they are designed that way). I suspect the bargain price reflected that problem. However, I'd send it back or take it to Naim, who are in just up in Salisbury, and might sort it for you while you wait.
If you decide to keep it, you can buy a cheap phonostage (see post 8), which you plug into the Aux socket on the Naim and then plug your turntable into it. This is a common thing, and any dealer can advise.
As people suggest, if you do send it back, try to find a Rega Brio, which will work well with your turntable ... it's a simpler solution.
A lot of the
'old-timers' haven't heard modern Naim amps, and are basing their comments on older models, which could be a little 'strident' in their sound. That is not the case with current models. I have owned both current Nait 5si and the 'previous generation' Rega Brio R, and the Naim is marginally the better amplifier, but the Rega is better value.
Hope that helps