That's a Rega for you!!!!!
The top model(s) do have some extra motor shielding, but the main range models have never had this - ever - and some cartridges, especially their own MM's and Grado's I remember, are sensitive to this, as fully shielding the cartridge all round would reduce it's output (I was told by Roy Gandy when discussing the Bias, Elys and Exact models in particular).
One thing regarding equipment racks if you use one... Can I ask you to lift the deck off its support and see if some of the hum reduces? Roy G was adamant that hum is additive, and a nearby transformer hum field can add to the field from the motor and make a tiny issue into a problem.
You could get in touch with your local dealer, take the deck there and see how it compares to their demo one in a different system.
Usually, careful cartridge choice renders this a pretty well non-issue, but it does rear its ugly head from time to time.
Tear down these walls; Cut the ties that held me
Crying out at the top of my voice; Tell me now if you can hear me