Never mind, dotty - and they're not allowed to age discriminate any longer! I went for a really nice job a couple of years ago, but I didn't get it (like you, "the calibre of applicants was very high, and others had more relevant experience", and with hindsight I am really glad I didn't, I wouldn't be where I am now.
However, I did contact them and ask for interview feedback, and they sent me some really comprehensive feedback which was very useful for another time. Worth asking for that re your own interview.