FullWings is hearing correct.
Some travellers/visitors to Europe from distant places (capital city !!!) are indeed making travel plans to avoid the very high UK APD, lets say they visit the UK first, then mainland Europe and depart home from there, if they research UK train costs, maybe some will skip the UK.
My previous point about Trains and Planes and costings, the UK has expensive trains, getting more and more so, if the UK public can pay for the expensive trains, they will pay more for air travel, simples ???
I think some Euro countries held air travel tax and even suspended it, poss Holland.
The sooner all Euro APD charges are collected by BRU and handed out as they (BRU) see fit the better it will be !!!