I like flying and fly reasonably frequently - usually up and down to Scotland to visit family for weekend trips but other holidays too. I've done some UK trips but, to be honest, as a single or when travelling with friends, it can work out far more expensive with less guarantee of weather/friendliness/change than going abroad to widen horizons and visit overseas pals.
I take the train to Scotland for longer breaks but it just doesn't work as well for weekend trips - I tried it again recently and it was the worst trip north/home in years.
The flight is about the same price if you book at the equivalent times - but I don't have to leave work early and I arrive in Scotland earlier on the Friday evening. On the Sunday, I can leave Mum's after having an evening meal and be home by 11ish. The last time I caught the train, I left 90 minutes earlier and got home at 2am.
Not to mention that you end up travelling over mealtimes and the buffet cars/restaurant cars aren't always open (or have much other than a toastie in them). I appreciate you can take your own but the National Express East Coast have a 'meal' service that only runs from 1-4pm which seems a little ridiculous. Not particularly useful on a train where everyone is coming from the office on a Friday night and will be on the train til after 11pm.
I don't own a car so take public transport/walk most places and I pay the carbon offset fee on the flight so don't feel horribly guilty about preferring the convenience.