Just to give you a heads up on your dilemna. I bought a Maltese import WRX STI about 6 weeks ago. It has a conformity certificate for the UK and as such my car was first registered new in the UK. After reading up the legal standing on this, it means that you can declare the car as a UK version, as it was new at first registration in the UK.
The car was in mint condition and had an aftermarket touchscreen Sat Nav and audio system worth £2500, so it worked out to be a good bargain. The car has had 13 services, when it only needed 6, so it has been well looked after. The last owner, of 4 years, only put 8,000 miles on it. My car also has the laserline alarm fitted with a Cat 1 certificate.
Betweeen 2004 and 2006, Motorpoint and other such companies imported hundreds of these cars and sold them for up to £3000 less than the UK versions. The playing field was levelled by Subaru UK soon afterwards, as they were losing a lot of customers'.
The only differences were that the Euro spec version did not come with DCCD as standard but it was offered as an option for approx £1200. To be honest you really won't notice the difference of not having the DCCD and there are a number of articles claiming that the Suretrac front diff is actually better than the Helical diff, which comes with the DCCD equipped cars. Also the seats don't have side airbags but as a result are much thicker at the side, so more comfortable. It also did not come with an alarm system as standard, so most buyers had Cat 1 alarms fitted. A point of note when the cars came off the production line in Japan they weren't fitted with alarm systems, rather it was IM (International Motors), the offical UK Subaru importer who had Cat 1 Sigma alarms fitted to the cars here in the UK.
Other than this the cars are exactly the same including;
-Longer wheelbase
-Wider rear track
-Upgraded suspension components and geometry setup
-New interior including fully automatic climate control
To clear up any confusion with reference to the 2005 model year, which had all these enhancements over the previous model, the 2005 model became available to buy in the second half of 2004. The easiest way to spot them are that they'll be on '54' reg plates and visually, will have the rear wheel arch extensions.