Hi Nick / Roger.
The stopper with heart canes is, I believe, a Whitefriars stopper from around 1950, just when Walsh Walsh finished, and some workers migrated there. A few years ago I had a bottle with a very similar stopper, including heart canes - but the base had canes which were a strange mix of Whitefriars moulding and Walsh Walsh 7/6 centres. I think it was discussed on a thread on this board some time ago, and some of the canes in my bottle turned up in examples of Whitefriars Triplex and EIIR 1953 weights. I also had a paperweight with heart canes - see image below - at least two different canes match your stopper.
Coincidentally, I took the bottle back in part exchange recently, so once the dust has settled on the PCC AGM this weekend I should be able to take some new images of it.