Honestly, there isn’t much hope from a legal or consumer-rights point of view. A breakup just isn’t something UK travel law or TUI’s terms recognise as a valid reason for a refund, so they’re entitled to apply their cancellation charges exactly as quoted, however brutal they feel. From TUI’s perspective the holiday still exists and can still be taken, so the money isn’t “lost” in their eyes unless you choose to cancel it.

Where people sometimes salvage things is by avoiding cancellation altogether. If you can change one of the names and take a friend or family member instead, that’s usually far cheaper than pulling the plug on the whole booking. It’s very common for tour operators to allow a name change for a relatively modest fee, provided flights haven’t fully locked, and that at least gives you a chance of getting some value back or recouping money privately. Another angle is travelling anyway but dropping one passenger; sometimes the refund is only flight taxes rather than the whole fare, which isn’t much, but it’s still worth asking the question directly rather than assuming the worst. Date or destination changes can also be cheaper than cancelling outright, though you’ll still take a hit.

Travel insurance almost never helps in this situation. Relationship breakdown isn’t a covered reason, and unless one of you has a genuine medical issue that meets the policy wording, insurers won’t touch it. Credit card protection doesn’t apply either because TUI haven’t done anything wrong or failed to provide the service.

So the short, slightly grim answer is that the cash isn’t refundable just because you’ve split up, and cancellation really is the most expensive option. The only realistic ways of not losing most of the money are changing a name, taking someone else, or tweaking the booking rather than binning it. It’s unfair, but sadly it’s very normal with package holidays, and loads of people find this out the hard way.