I still fail to see why the piece of paper for an identical item can add so much to the cost -in our case over 35%
Lack of access to information
In GA, often the most appropriate saying is: in the land of the blind, the one eyed man is the king.
The other thing, of course, is that if you bought that $9k prop, the maintenance company is not going to make the margin supplying it (say £2k on a £11k supply) so their only income will be the installation labour at £50/hr or whatever.
One can make similar huge savings on avionics by importing from the USA - of the order of 40%, after allowing for VAT and shipping. But no major avionics shop will install the item, so this practice is limited to hands-on owners who work with a one-man installer who is probably happier not supplying the hardware as doing so would push him above the mandatory VAT threshold.
The downside is that there is no meaningful warranty on US imports, in that you cannot practically sue anybody. You can return the item... OTOH any warranty implementation in the UK tends to involve a flight to the installer's airfield, which (especially with hotels) is going to cost way more than whipping out the item and sending it back to the USA by DHL...