Importing parts
Maybe I'm going to sound boring, but VAT and Import Duty is the law, everyone should expect to pay it. If you don't by chance then good luck, but if you bring in items of any serious value and try not to declare it that is illegal and you can be fined and even jailed if doing it in volume. Anyone who runs a business will know that Customs & Excise have more powers than the Taxman and are even more single minded about getting people. You risk VAT avoidance at your peril.
As for buying parts from abroad, not the UK importers, once you have paid VAT and Import Duty, you will find you have saved little if anything. You also run the risk of non-arrival of goods or late arrival (7 months for wheels quoted elsewhere!). Also what happens if its the wrong bit or the part goes wrong. Most Japanese direct suppliers eg Taka Kaira/CheckerFlag have a policy that when it leaves them they have no more responsibility.
I have had a major piece of kit that cost £2000 supplied to my car that was faulty from manufacture. Since this was supplied by the UK importer through my tuner, I was able to hand it back as faulty and have an alternative piece of equipment fitted by the garage for no extra charge. This is the quality of service you will get from using a reputable UK tuner who sources their parts from a UK supplier. If I had bought that part direct, I would have no recourse, would have lost £2000 and would probably have had to pay my garage to remove it and fit a new one.
Be aware of this when deciding to import parts direct. You might be OK for an air filter or some cosmetic parts, but think carefully and weigh up the advantages and disadvantages before buying any expensive or mechanical/electrical parts yourself.
It also serves none of us any good, if we drive the parts suppliers and UK garages into bankruptcy by trying to be clever and save a few quid.
You pay your money and you take your choice, but think carefully about what happens if it goes wrong and you might find the little extra to buy here (for most stuff) is worth it.
Well thats my thoughts anyway.
Guy