It's a few years ago now but I know of one former ATCA (as was back then) who took five or six attempts before being successful and who ended up as "Top Cadet" (as it was also known back then) and also successfully validated at LHR when it was both twr and app.
The moral being, if you want it badly enough don't give up. Keep trying and don't take no for an answer if at all possible.
Good luck.
WF.