((The anomaly is probably consuming energy to power itself. Firing lasers at it would make it grow faster.))
(( That depends on what it is, honestly.
If it's a section of super cold space, then what we're seeing is all the heat from the surroundings rushing into it, and firing into it will increase the amount of heat it has, slowing it down because the temperature gradient is less. This is also why it could slow down as it expands, because as it expands it's taken in more energy, and taking in more energy more quickly, so same effect.
If it's the manipulator trying to keep itself as cool as possible, and it is drawing from an infinite high-science power source and not the heat energy from the surroundings, then much the same thing happens, only it becomes a rate thing instead of an average temperature thing. When the sphere has expanded to the point that the amount of heat going into it is roughly equal to the amount of heat the manipulator can get rid of, we'll start to see things similar to the above. If it's working off a finite power source, then it can also only do this for a limited time before it has to move to option 1) 'a really bloody cold section of space'. Either way, if you can maintain a continuous stream of heat into the space, then you'd make it so it will reach that tipping point sooner.
If it's the manipulator trying to keep itself as cold as possible, *and* one way it is doing this is by consuming heat energy, such that it can always dump more heat than comes in, then we're pretty much screwed.
If the manipulator has generated a section of absolute zero space, Steve help us.
Yay napkin physics! ))
((Not to mention that heating up a small part of supercool material would cause a huge ass explosion when that part suddenly expands. And the possibility of friendly fire. But this is the HMRC. They're not supposed to worry about logic, safety and other silly stuff.
Edit: Although now that I think about it, they have all the tools they need to keep themselves safe if I understand how the laser batteries are supposed to work.))
(( I'm betting that's where all the ice shards are coming from, so hopefully the added energy wouldn't be too ridiculous. And steve could always add it on the township side.
))