Swiss company SIG (sold to Fiat in 1995) came into it somewhere.
Most Pendolinos produced by Fiat/Alstom use hydraulic actuation for tilt, but 390s use electric actuation developed by SIG.
The SIG tilt system is also used on SBB's ICN trains which have been running for much the same time as our 390s.
The Fiat/Alstom hydraulic system is also used in trains not normally thought of as Pendolinos, such as DB's ICE-T trains.
The tilting system on the WCML also required the development of TASS (Tilt Authorisation and Speed Supervision) because our smaller gauge does not allow "tilt at will" as used on the continent.
This required a form of cab signalling, and the installation of the linked balises in the infrastructure to control tilt operation.
That cost is specifically down to the 390 programme (it's also fitted to the Voyager class 221 fleet which also operated on XC routes).
The TASS system was developed by Alstom.
So the 390 tilt costs are a complex amalgam of SIG/Fiat/Alstom development on the generic design, plus specific localisation for the UK operation on the WCML.
Most of the cash was put up by private shareholders, and is reflected in the leasing and maintenance costs for the trains.
The 390 was not a "BR" train, it dates from after privatisation.
The main British element of the design was the traction package, developed at the ex-English Electric works at Preston.
There are also pure French aspects of the design, as you would expect from an Alstom product, but these are not related to the tilt function.
The initial (2002) tranche of trains was assembled at Washwood Heath, with major components like bodyshells and bogies coming from Italy and France.
The later (2012) supplementary order of 106 vehicles (4 complete trains and 62 vehicles to extend 9-car trains to 11-car) was assembled abroad.
Although this might seem a rather complicated history, you would find much the same kind of thing if you investigated the origins of most new trains today.
If Alstom succeeds in its bid to acquire Bombardier Transportation there will be another twist in the global supply chain for new trains.