I was in there today, and it is indeed freezing, and I really admire the stoicism of the staff.
It doesn't make sense that its down to HR to fix the boiler-though it may be an HR issue regarding giving out extra uniform, body warmers mittens etc.
I certainly hope that the staff receive a decent bonus and time in lieu or extra breaks for putting up with it-as my understanding is that if its below a certain temperature they are within their legal rights to refuse to work.
Where I work they have a staff member dedicated to taking temperature readings in every dept 3 times a day, however having said that we were all baking hot today but were told that the reading was within accepted parameters...wish I could have bottled some of our heat and given it to Sainsburys!