That image is how it was as i found it directly behind the plaster. Above is the loft, that’s a stud wall effectively. I can’t see a reason why they are there, the bricks are sat on the wooden base of the stud wall, which is sat on a supporting wall Sounds odd, but to hold the wood down and keep it from warping maybe?
Strengthen the wall is what I was thinking, provided fixing points to hang your radiator and whatever else on that wall. Do you have anything fixed to the wall the other side, thwarts relying on the bricks for support? Can't see why they can't come out, they look to be long redundant now.
Nothing at all on the other side. this room didnt even have a rad til about 10 years ago so it’s a bit weird, only seems to be the bathroom walls too, none of the other walls upstairs share this. I’ll have them out tomorrow, if you don’t hear from me, assume they were a key part of the structure and removibg them caused the house to come down ontop of me!
Bricks on edge were sometimes used inbetween the studs on older partition walls. It was just an infill which offered better soundproofing, but not structural.