I have on each occasion prior to checking into a BRG reservation emailed regarding upgrades and most have stated a BRG is not different to a paid stay. Hotel indigo in Earls court told me they wouldn't upgrade me and I had to get the BRG team to correspond with the hotel to advise them this was not the case. After a few emails they accepted it would be treated as a paid stay. I assume this was possibly the case with this particular hotel as they are fairly new to the chain and unaware how to treat a BRG stay.