Sounds like I got off lightly
My pension was taxed at BR from the outset and at one stage I had tax codes for 3 different sources, all penalising my tax-free allowance on account of the others, and even adding in the other odd restriction by inference (business phone).
After a couple of years I managed to get rebates at the end of each Tax year, only to be handed a demand based on the same scenario as the one I had just been over-taxed with.
Calls to the tax office (40 mins waiting each time) would furnish me with a new set of tax codes - only to be countermanded a few days later by another set of erroneous ones.
9 years later, my accountant managed to get through to a knowledgable grown up at HMRC and has got them to accept that I declare all my income in each year's tax return - and my pension is now paid without an abatement.
The whole thing smacked of poor outsourcing; disjointed departments and a lack of expertise at the coal face - often a symptom of a poorly-specified outsourcing contract.