wow, it seems I accidentally resurrected this post after googling "loud bang Wirral". I was at work on Thursday 5th June and heard a massive bang as I walked across the factory to speak to a colleague. The bang sounded quite far away, possibly out to sea. It shook the roof of the factory and caused a load of dust to fall from the office ceiling. Some of the office staff came out including all of our top brass to see what was going on as they thought one of the shop floor staff had blown something up or injured themselves.
I spotted a right noisey b*****d jet flying over a while later, which I thought at first was a Harrier, but might have been a Tornado with its wings swept back flying away from me towards Liverpool.
However, I was always under the impression that a sonic boom is only audible from behind the jet and only at close range.
i think the bangs you are reffering to are the docks in bootle.
They are resizing the docks, making them bigger, my uncle lives on new brighton front and his room shakes with the booms.
i saw the harrier fly over our work too, being close to the sea we see them quite often.