March on Downing Street, just as the police did. The march would be for ex-serving, families, friends and supporters of the Armed Forces...but crucially, also serving personnel (in civvies).
The precedent of the cops marching blew the argument of "political neutrality" out of the water and the only way things will improve will be if significant public opposition is mobilised. This sort of thing would get tens or hundreds of thousands marching.....there is an enormous amount of support amongst the public and plenty of serving and ex-serving within travelling distance of London. Add to that the organisational experience, drive and initiative of organisers. This CAN happen!
If enough march, then it will be impossible to charge or take administrative action against participants due to weight of numbers.