UPDATE - a new plan.

Hi all, and thanks to all who have responded so far.
I have thought long and hard today about what I should do and taken on board many opinions, both from replies here and in chat and I have come to my senses and realised that sending the letter would not be a good idea. To do so at this point would make it blatantly obvious that I was pining for S and I could do with keeping the parental suspicion to a minimum.

So I have a new plan. I will try to concentrate on the exams for now (sorry Strider - its not as easy as you make out - these are important and resits aren't practical, however much I love her) and in just less than two weeks time go back home and attend a scout meeting. I will not announce my attendance beforehand so the parents have no reason to prevent S from going, thinking I will still be absent. There I will assess the damage that has been done.

If she is back to how she used to be and we can be friends again in the scout group then I will carefully try and consolidate that into a friendship that can be extended outside of the group with parental permission, maybe to the letter correspondence as already mentioned.

If however she seems uncomfortable with me from the brainwashing process then I will approach the father only and voice my concern for her. That is where I need to pull a good argument justifying my friendship with an 11yo but I have time to polish that argument til it sparkles. If he is adamant that a friendship is still impossible I have no choice but to leave it but at least I get to say my goodbyes.

To all the people who have suggested merely running away - It isn't possible. Love is one of the strongest emotions around and it will never be ruled by common sense!

I'll post an update in a few weeks for those who are interested.
TTFN
Foreverman