Hi sealo0: they dropped to low level over Salisbury Plain, stayed low level to the south coast before turning eastwards along the south coast (below 1500' just offshore Bournemouth) before turning out to sea just east of the Isle of Wight and climbing back to FL280 for the return to Belgium.
By they way, the lead aircraft showed up just fine on ADSB Exchange, which doesn't filter out military or bizjets, and has a neat replay function.