Most companies will ask you what level of cover you require, from baggage insurance to personal effects. Ensure you know the value of that you are taking away with you, but also consider the value of goods you may be bringing back. You may have to claim for them, if they are lost during the return trip.
Many low cost airline operators do not compensate for late departure or cancellation, the most they will do is transfer your ticket or refund the ticket price. They recommend your have over 65 1 stop travel insurance to protect you financially from these circumstances. Of course many offer their own policies online when you book.
A serious illness can happen abroad, but where continued treatment is needed back here in the UK. Sometimes special travel arrangements have to be made, as normal air transport may not be able to handle the movement of the patient. There are special planes adapted for this reason, with specialist support. But this is very expensive, something most of us would struggle to pay for. Look to see if your travel insurance covers you for this transportation.