I highly recommend it, as a ex-pom I buy most of my bits over there as they are still miles cheaper even after post. There are heaps of old minis over there and unlike oz they are not seen as rare or unique vehicles so the prices are good. SU, Lucas and Smiths bits are especially cheap as just about all british cars used them.
Italy can be good too - the had innocenti built minis
Only buy from sellers with PayPal or Credit Card - Bank Cheques cost around $20 and the post office does not recommend money orders under $150 because of changes in exchange rates.
As for postage there is a massive difference in the prices between air and surface
if you are not in a hurry surface will take between 6 to 8 weeks but will cost about a quarter of the air price. Air prices are quite steep but you will get your goodies around 10 days. Use ParcelForce - they deliver to the post office if you are not a home.
Customs over $400 as Wombat pointed out 15% plus GST - ask the sender to decalre them as second hand and understate the price if possible.
