Hi Freddie
Congratulations on taking the plunge - that is the hard bit done. I think it's probably best if you ask any specific questions you have as there are so many possible ones and it is hard to know what you have already been given advice on but here goes some very general stuff.
Firstly, the airport. Make sure you get to Gatwick with loads of time to spare. Normally check in for Europe is around two hours and your info package will tell you that but depending on how far you have to come I would allow at least an hour more maybe two. You need to allow for any travel hiccups on the way down, whether it is traffic delays, train issues etc - there is nothing worse than the panic that you might miss your flight. There is loads to do at Gatwick - shopping, eating, people watching etc and I like to think of that as the proper start to your holiday so the earlier you start the better! You might also bump in to your fellow passengers and start getting to know them. Also, make sure you know whether you are flying from the North or South terminal. They are linked by a monorail.
Don't forget the rules about liquids on planes. There has been a suggestion of them relaxing the rule but nothing has been announced yet so look on the Gatwick airport website which will advise on what can and can't be taken through Security. I always buy a bottle of water once I have gone through security for the flight so that I don't have to bother the flight attendents.
If you have any nerves at all about the idea of flying it may help to let the flight attendents know that - they are very good at putting people at ease.
With regards to clothes and what to pack - have a look at any previous posts on here to see what has been suggested. Also, once you know your hotel you can look online to see what facilities ie hairdryer, tea & coffee etc they provide.
You will be told in your Info pack when you are meeting your Just You Rep - this may be at Gatwick or at your destination. They will look after you brilliantly and deal with any problems or concerns you have whilst on the trip.
I guess the best advice I can give is to relax and enjoy the whole experience. Hopefully some other people doing the trip will post on the forum so you can chat and get to know them a bit first. That always helps with the nerves at the airport as you feel like you know them already.
Sally