As a Senior you probably have a lot of freedom as to when to travel and so can make very good savings by, for example, travelling mid-week. For advice on the best times to travel, see Fly on a Tuesday!
Although reluctant to recommend any airlines (I’ve had so many problems with the flights I have taken over the years), the intercontinental airline I’ve found most satisfactory is Virgin Atlantic; they also seem to have much better cabin service than most trans-atlantic airlines. To avoid the busy London airports, I often fly via Amsterdam with KLM; this can also be a cheaper option to some destinations.
I often travel to Eastern Europe and find that both Jet2 and easyJet have good coverage from the UK, including flights to Budapest, Dubrovnik, Krakow, Ljubljana, Prague, Pula, Split, and Zagreb, and both can provide a holiday package by adding on competitively priced hotel accommodation.