From what I've heard, it's still early for bloom in the UK. Flowers will appear on the first flush of new growth in the spring, provided that the terminal buds haven't been killed by frost. Anything on older wood that looks like "buds" is actually seed capsules, which can persist on the branches for decades.

Apparently ,in Australia, these plants wait for fire; then this gets the seed to germinate. When I gardened my sister in laws garden, her bottle brush plant bloomed its socks off one really hot summer.....so perhaps your plant is waiting for a scorcher?

From what I have heard, they even need a fire to get the seed capsules to open. Some of the pines and junipers here in the American West are the same way. Bottlebrush does need some heat to really thrive, but we are actually getting too hot for it here in the Valley of the Sun. Always changes.