... do you tell the travel insurer (now Aviva, formerly UK Insurance Ltd) about all your pre-existing medical conditions?
My understanding from past phonecalls (UK Insurance) and current website (Aviva) is that it would cover pre-existing medical conditions if you paid for an upgrade. However, if you don't tell them about a condition, it won't invalidate your entire insurance (like some products), it just means you're then not covered for that particular condition.
Is that your understanding too?