I don't know the current lag. The greater the number of tests the more the lag.
However with the tests priority is given to processing samples from those whom are more likely be infected, or who are more known to be at risk, or where they are in essential positions or high risk environment (ie healthworkers).
Just anecdotal evidence, neighbours of my partners mother, who are in hotspot postcode were tested when those postcodes were initially shut down, with cold like symptoms. All four tested on the Sunday. The three with D/L address at that address had results on Monday, the one with D/L outside the lockdown area didn't receive results until Wednesday. So it could be a mixed bag with lags. (BTW all negative).