Evacuation tips:

Evacuation may include schools, even if it is just your decision to get your family home or far away. You should agree in advance who will collect the kids.
For a disaster that does not take down the grid but forces you out of town, what happens to your job, education and healthcare?
In war, tensions may have risen recently, meaning Brit Cits were repatriated creating a housing crisis affecting your ability to move home.
In evacuation, authorities may try to force you out of your car to prevent congestion or to take strangers to fill empty seats.
In a mass health or injury event, ambulances will no longer transfer you for appointments so you will go without specialist treatment. If a hospital is evacuated, it can take two years to recover, even if society continues business as usual; that is how vulnerable they are.
If a school is evacuated, teachers will keep children with them rather than send them home so you need to find out where and get there.
If a prison is evacuated, it is to the courtyard and if that is not viable prisoners will either be moved by NOMS under outsourced contracts or if NOMS are incapacitated then presumably released. Immigration detention centres rely on the Prison Service to help in an emergency, which may not be available, meaning they are more likely to open the gates.
If a zoo is evacuated then non-native animals have to be locked in by law – which would appear to cover tigers etc.
If the council evacuate your home it will probably be to a hall such as a school or leisure centre for which your bug out bag (‘BOB’) will be handy, especially if topped up with ready to eat food, a sleeping bag and mat (and blowup pillow such as a ziplok), toiletries and change of clothes, as these would take time to arrive even if a calloff contract was invoked and could deliver. Apart from food and bedding, the same applies if you can make it to a distant friend or relative or hotel.

Oh dear: Council disaster preparedness experts ‘advise’ on grab bags

History shows that council evacuations are chaotic and even moving the equivalent of just one street will be messy. Look at what happened when Grenfell tower had to be rehoused after it turned into a funeral pyre and similar fire risk towers emptied as a precaution. You are chucked on a gym floor in the clothes you stand up on the first night and then you might get a B&B in subsequent days.

The Housing Acts require councils to house their whole district if made homeless for more than a few days by disaster, so they would have to use their contingency fund to send residents to other districts and hope government reimburses them. Council have a power to provide shelter in the short term, which mean rest centres or hotels.
In a local evacuation councils may try to get wardens to patrol the district to persuade you to leave your home unguarded, but they are unarmed and currently have no powers beyond ticketing for dropping chewing gum etc.