Yup, that Blue Trongate building I've been modelling is having open days on the 26 and 27th of June. Doors open on the hour, every hour, between 12pm and 4pm both days. Entrance via New Wynd at the right of the building.
For details and to book your place, go here: http://www.glasgowmerchantcity.net/britanniaopenday2606.htm
Well worth it!