Quote 1:
"[Q] Can You Freeze Bubble & Squeak?
[A] Yes – simply portion it up in any freezer bag or box and put it in the freezer! When cooking, you can cook it from frozen, but you’ll need to add about 10 minutes to your cooking time to ensure it’s not frozen in the middle still. It’s better if you can defrost the bubble & squeak before cooking it."
Source:
http://www.foodcheats.com/microwave-bubble-squeak-side-dish
Quote 2:
"How to Cook Bubble and Squeak From Frozen
This is the simplest method to use your frozen bubble and squeak. Just take it out of the freezer and fry it up slowly. Using this method means you don’t have to fry up your bubble and squeak before freezing and you still get that lovely fried taste and texture"
Source:
https://www.freezeit.co.uk/can-you-freeze-bubble-and-squeak/
All the same (if anyone could persuade me to eat the revolting stuff in the first place), I'd defrost it in the microwave first myself.