Wheelbarrow
I'm not involved as aircrew anymore (and that was military), but my ground jobs have involved discussions with taxmen.
Each officer has a good deal of power and interpretation. This can be useful when they find in one's favour, but a pain as in this case. However, for the rest of the country, one taxman's decision does not set the rules.
The best way to get a resolution, which might just be painful to those not being hit by this decision (yet), is to check the ruling with HMRC head quarters and/or ask the guys you are dealing with to quote the regulation they are using.
If you are a BALPA member, or in any such union, it might be best to get them on the case.
Rgds
O96