Re: HMRC is a governement department...
"Is this some sort of ruse to deguise employment by a government dpartment that can avoid Civil Service pay and pensions obligations?"
Yes. Like it or not, Cap and Fujitsu staff have got oodles of experience running HMRC's systems. Many of them were EDS before they were Cap/FJS and have been there donkeys. They simply will not work for a civil service salary. A dev team lead, for example, would be looking at dropping from the 50-60ish range down to 35. On the plus side it isolates the pensions obligations, but frankly a lot of these guys have been TUPE'd about so many times they've managed to accrue both private sector pay and public sector pensions.
The end result is this new pseudo-private body has mostly only managed to recruit the woefully underpaid apprentices and other similar junior staff. Everyone else took one look at the terms and conditions and said no thanks, safe in the knowledge there'll almost certainly be a nice juicy round of £700 a day contracts to keep the lights on when the plan inevitably goes tits up.
"When did any of us consent to that Data Processor dealing with our data?"
You don't have to. There's no requirement that the Controller seek consent for using a third-party Processor, as long as technical and organisational measures are in place to ensure DPA compliance. The burden for doing this remains with the Controller at all times, and if the data is being processed to satisfy a statutory requirement, the Controller is *always* the statutory body.
tl;dr they can do what they like with your data but it's on them if anything goes wrong, no matter what contracts or organisational measures are put in place.
Biting the hand that feeds IT
