Travel Agents - different rules for different customers?

[Bakedbrie]

This seems weird to me. Booked a Package holiday Last September with a Travel firm to go away end of Coming August - long haul. Paid a low deposit of 500. If I cancel now before paying balance, firm states I loose my deposit - due to Covid risk. Firm says package still available. No commitment to refund within statutory period though. Balance is 6K, a lot. Not an uncommon scenario for many right now, right?
BUT for NEW bookings, same firm advertises on their website to return all deposits if holiday cancelled due to Covid! How can they have one set of T&C’s for one set of customers and another set of T&C’s for a second set? Is this even legal?

There is nothing legally wrong with a company changing its terms and conditions. New customers get the new Ts&Cs, existing customers stay on the old Ts&Cs.

It isn't clear to me if the new Ts&Cs are actually different. Your holiday is 3 months away. It isn't cancelled due to Covid. I expect their Ts&Cs refer to the situation where it is clear the holiday cannot go ahead due to government restrictions. That is not yet the situation for your holiday.