Ill give you a couple of differing experiences.
We have been with Club C a few times. The best experience we had of their reps we has was when we went to Antibes in S.France. They were excellent, and couldnt have been more helpful. However, when we went on a couple of occasions to Italy with them, the reps were pretty awful, although i always felt that this was more to do with the fact that one person who was based on the campsite had to cover the 3 hotels also, which were at various places along a 10km strip!!!!!! We had probs with the hotel meals (me being a veggie) and after getting a bit fed up of having problems a few years previous, i wrote a letter asking why i was being treated in that way, and the reply from Club C wasnt exactly nice, saying that they had put plenty effort into what was a 'bucket and spade' holiday, and advised me to look elsewhere!! Way to trash their own holidays, eh?
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Well, i did, and have went with Redcrest ever since
However (getting back on track!) i think you will find that the reps on Castell Montgri will be fine, as they are close by to where you will be staying, my problems with the reps were because of the distance the poor sods had to cover, and when i was in the S of France, the Reps were great!
So relax, and have a good time, to be honest, you dont really need the reps that much anyway!!! Better to get most of your info from this great site, and if you want to see some pics and views of Estartit, click onto my website, plenty of pics on there!