I took my 14 year-old daughter to Andorra on the little yellow train -in the 90s. Amazingly memorable! I must go back and do it on my own. We stayed in the YHA at Perpignan (why the red underscore for the word 'Perpignan'?) -for a couple of nights -on a 10 day tour of Southern France which also took in a stay at the YHA at Vichy. TGV transport to and from -with Eurostar doing the other bit to what was then Waterloo (now St Pancras (another red-underscore) -of course.