Slok are a Nigerian outfit - have also heard the 12 acft story - so far they have no acft that anyone has seen and have never operated except for a short lived cargo operation in the late 90's where they chartered a 707 - lasted 3 days and the plane never flew
It is not a question of the airline getting 'un-banned' as in this case the UK authorities have acted because they do not consider Gambia CAA is carrying out (read is fit to carry out also) its safety oversight responsibilities/regulation in accordance with ICAO procedures/statute - only way is for GCAA to prove they know what they are doing, put a long term action plan in place and be subjected to both UK and ICAO inspection and ongoing audit...you could be waiting a long time