A couple of quick points.
1. No TU can "instruct" its members to do anything. They could only do that in the past when there were closed shops. Only the RMT tries to do that nowadays. BALPA asked its members what THEY wanted to do about BA. They replied more or less unanimously. The "Instructions" were from the members to the TU.
2. The word "average" is being misused. The BA pilot total fraternity have average pay of roughly £100k.