It is next door to the Tesco and has a front and back entrance, i've never gone in the back way but have left that way a few times.
The front door is red and it's set back from the road / pavement so basically as soon as you turnoff the pavement you have your back to everyone, just press the buzzer / intercom and they normally release the door straight away, pull it and your in then go upstairs to reception
I actually find the front way nice and discreet as you just walk down the road, nobody knows where you are going until the last second when you make a 90 degree turn but they can't see your face by then
Same coming out, one you are on the pavement and 20 metres down the road you just merge with everyone else
Depending on the time of day the back way can be more obvious especially if Tesco are having a delivery and half a dozen people watch you going in / out for longer knowing full well where you are going / been

My advice is to walk down the road and work out where it is 1st as a sort of dry run then you can decide which way is best for you on any given day
