Sentinel 7109's boiler is supported in the cab on four brackets around the firebox.
Four Fixing brackets (there's another round the back)
Three fixing holes (rear set)
It is held in place with seven longish and three shortish bolts about one inch in diameter. The longer ones go through the footplate floor; the shorter ones through a thinner supporting bracket towards the cab front. In a pretty dilapidated state, I've cleaned them up using an electric drill and wire brush.
Before (LH) & after (RH) brushing-up
Judging by the state of the top ends, which presumably had the hole through to take a split pin and castellated nut, they required a certain amount of violent percussion to remove them when the boiler was taken out. Despite their state, they are probably adequate to reuse. Anybody seen the nuts?