Are there any course available abroad where you can learn to glide, say over a week, and make a holiday of it? Or is it best to learn beforehand?
Several Dutch organizations offer mid-week (mo-fr) courses with the opportunity to camp (tent/caravan) on-site. I assume that the same thing takes place in other countries, and in the UK.
I did one such week at Salland last year and am going to do another one this year. Price is 310 euros for the full weeks course, including 15 winch-launches but excluding insurance, camping fees, breakfast, lunch and dinner.
Beginnersopleiding - Aero Club Salland
The other place in the Netherlands that offers a lot of these packages is Terlet:
Nationaal Zweefvliegcentrum Terlet
Of course, when you come to the Netherlands the dominant language will be Dutch. You need to inform specifically if they're going to be able to accommodate English-speaking students.