I've been informally checking Rega decks for speed accuracy for the past year and of my admittedly small sampling (11 units to date), I have not been able to comfirm any consistant pattern of speed deviation for these turntables. All were decks owned by friends or clients and nearly as many ran spot-on or slightly slow as did those that ran fast.
After replacing the belt and cleaning the pulley, only 2 units had a speed error in excess of +/- 1/2% when set up level & playing a record.
IME, the primary factor in Rega speed appears to be in keeping the motor pulley clean in conjunction with a well maintained or fresh OEM Rega drive belt.
At this point in time, the elevated speed issue appears to point to belt inconsistancies(esp non-Rega sourced belts),wear or improper viscosity lubrication & maintainence. I also suspect that local variations of the AC mains supply may also be involved in the reported speed issues as one of the units tested ran slightly fast on the first occassion and at a correct speed a few weeks later in a different session.