The thing is, you and your colleagues have a card to play: if it wasn't written in your contract and you've been working that way for two years, it's become an established practice. Your employer can't just throw a change at you overnight without negotiating - they have to give you a notice period (several weeks minimum, not just a few days) and technically it's a contract modification.
If there are several of you in the same situation, you could ask for a collective meeting to discuss it, or at least send a professional email to your boss saying you're asking for a transition period and maybe some flexibility (like 2 days in the office instead of 4, or a hybrid arrangement). If he really refuses to discuss anything and it's a problem for you, you can consult an employment lawyer or contact the employment tribunal, but honestly, most of the time just raising the issue politely makes companies more reasonable about the timeline and conditions.