I did this exam 12 years ago, and certainly recommend it as something to work for. I chose a programme off the syllabus to save the time that would have been taken to get own choices approved. As with all diplomas, the key to success is to walk in looking like a confident and experienced performer whom people would be happy to pay to see. I took the exam at Trinity College and the facilities were excellent. I don't know where you are located, but you could also look at the new ARSM diploma run by the ABRSM which requires a 30 minute programme, and can be taken at local exam centres (you need to have passed Grade 8 to take this). Both of these are respected in the UK. Note that if you want to do higher ABRSM diplomas (eg LRSM) you have to do the DipABRSM which has the same syllabus as the ARSM but requires a viva and quick study.
Many thanks!!! That was actually very helpful. Which ohne did you go for, the ATCL or one of the more advanced diplomas? Also, do you know whether these diplomas are known in the "professional world"? So, if I wanted to play a little concert (which I donīt aim for at the moment, but you never know) would this count as something you could write in your vita? Maybe not the first diploma, but the LTCL or the FTCL? I am currently living in Germany, but it wouldnīt be a problem for me to go to London in order to take the exam; I have many acquaintances there I would love to visit on this occasion.