No,Gatwick is your Alternate (fuel).
Search easa ops RCF, you will get the info and learn about RCF.
Long story short,you need to find out how to calculate your contigency fuel point,then if required,you can select a more suitable contigency alternate,an airport that would be within a certain radius of that point.(25 %of your flight plan route distance or 20% plus 50 NM).
Normally for flights above 2 hours,the latter is used.