Not been for 20 years now. I got the stage where I didn't want to drive there & back, 6 Hour round trip and a tankful of fuel used up. A lot of the Demo rooms are packed, hot, noisy, claustrophobic and because of this you don't get to hear (or see) the hardware at its best. The music played was not to my taste most of the time. A few of the reps who were there in the past were a bit snooty, when you told them what hardware you owned they would look at you like something they stepped in. I did buy a AV Receiver there in 2004, that has long gone.
Even if I did want to visit it would have clashed with my annual CPC driver training for work, that has to be a priority though I'm going to stop said driver training weekends in 2029, that will see me through until 2034 by which time I should have retired from LGV driving.
My priorities have changed now I'm 20 years older, Specialty coffee I'm into now. That's my annual trip to the London Coffee Festival will be my 11th.
Having said that, I did go to a Hi-fi show at a Heathrow Hotel a couple of times, If Audio T decided to hold said hi-fi show there at this time of year then I would think about going.