I had VHI travel insurance for the last two years. Its good value but depends on what type of travelling you do. I was in China last year and had connecting flights betweens flight from China to Thailand (an international flight) and my flight was cancelled due to adverse weather conditions. The airline refused to put us up / arrange hotel etc and we were stuck (as had only expected to be in airport for a few hours). We had to source a hotel for the night, get there and get back the next day which we paid for ourselves.
When I came home I called VHI to see if we would claim on our insurance - I was told we couldnt as it wasnt a qualifying flight. I didnt get a categoric answer from them however they implied that only the first outward and inward flight are covered on the insurance. If you travel long haul at all this could technically mean your Dublin to London flight each way and thats it. I'd double check this point with them if you go ahead.