I'd go for Japanese or French but it depends what you plan on doing later in life.
Japanese is what I'd pick, or Russian. Always good to get a change of alphabet somewhere!
I was about to say Spanish until I read you are not good at it, lol. So I'd say you should study French, because it is an important language, and quite easy to learn.
I'd kill to be able to speak Japanese or Russian.
If you're located in Dubai (and planning to staying in the Middle East), Arabic seems like a sensible option. Otherwise Spanish.
French is a safer option; you have done it before, and there is plenty of online help.
I'd say French because it's a useful language and you don't have to learn a whole new alphabet
Japanese/Arabic/Russian - interesting (only do it if you are willing to learn a new script)
French - the classic IGCSE language, lol . . . do it if you want to go to/are interested in France, French CUisine . . .
Spanish - Kinda similar to above, umm . . . do it if you want to go to/are interested in the US/Spain e.t.c
Basically, do the one you will enjoy! That's the best thing you can do - from your list am doing IGCSE Japanese and French
If I had that kind of choice I'd do one with a different alphabet.. think about the number of people who have studied French, German, Spanish etc.. and then Russian, Japanese. Speaking a language like Russian, Japanese, Mandarin, Greek etc. just looks impressive, in my opinion because it's not the sort of thing that everyone can do.
French will be one of the easiest languages there to gain fluency in as it is so similar to English. If you have any intention of working for the EU then French is necessary along with German. French is spoken all over the world. Possibly one of the most directly useful considering we're probably going to to end up in the United States of Europe.
Japanese, French or Spanish, personally I would go for Spanish or japanese as too many people are doing french and there is a shortage of people who do japanese, spanish, german, italian (and the list goes on..).
But it's really up to you.
I don't agree that French is similar to english.. the grammar is quite simple but actually vocabularly etc, isn't really similar..
I always found German a lot easier than French - 70% of the words come directly from English ("Ich surfe und chatte im Internet")
However, I'd say French as you don't have to learn a whole new alphabet and you say you're good at it.
I'm doing Arabic!
Its an awesomme language and easy to learn - go for Arabic.
i'd say french, only because i love it