I received a higher than expected quote from InsuranceWith and they would only give single trip insurance (ironically because my wife has a new non-cancer medical condition). 
Her Cavernoma support website pointed me towards this comparison site https://quote.medicaltravelcompared.co.uk/YourTrip
As a result, I received several quotes including one from the Post Office which was cheaper for annual multi-trip than InsureWith was for a single trip for exactly the same cover for exactly the same pre-existing medical conditions.

This proves that it is always best to shop around. 


Best wishes
Dave