Yeah I've heard of Open House Weekends but not the Scottish version.
A few years ago I went round the old BBC studios at Alexandra Palace on Open House Weekend
LWT/ITV House has never been part of London Open House - I should know, I've been going to them every year since they started back about 10 years ago.
Of the most well known broadcasting estab's taking part over the years
A free tour (same tour that was usually paid for) of Television Centre in the first year of open house.
Red Bee media centre - that was a Sunday only, and I never got to go around it
Channel 4. Reception, closed off offices, boardroom and staff canteen only.
Broadcasting House (so long ago the new wing was still concrete piles to just above ground level!)
ITN - atrium walkways only. The highlight of which was watching a very bored Steve Scott, on weekend duty on the ITN News channel, running through the O/S's on his preview monitor trying to find the lunchtime football game, before giving us a quick wave as we headed to peer into the old (but then still in use) 5 News studio/newsroom.