If you're not sure about a clearance, then ask ATC to verify the correct altitude/FL (before departure/ T/O).
Fine advice, but trot wasn't in any doubt.
On the licensing sode of things, if it's of any help, unless you have a licence issued by the CAA there's no licensing action that they can take. They may write to the issuing authority giving details of the incident but, as has already been stated, if you're open an honest and can show what mislead you I would doubt that anything serious will happen.