I think we had a thread on this a while back, but here's my 2c...
Depends on the size and value of the parts i reckon, and how they're being sent.
UK VAT is 17.5%
Anything brought into Aus in a shipment worth over $1000 should be charged customs fees of 10% and then sales tax of 10% on the total of the value + customs fees (forgive me if the names of these fees is incorrect)
So theoretically $100 of pre VAT goods in the UK would cost $117.50 in UK incl VAT
Getting it VAT free, then paying AUS customs fees, it would cost at most $100 + 10% = $110 + 10% = $121.
So theoretically will cost more.
Here's the tricky part though. If your mate buys it including VAT and the value is over $1000, it will then still be charged customs/sales tax, so could end up costing $142 per $100 ex-VAT!!.
There is a customs rule about goods to a value up to $1000 not being charged:
http://www.customs.gov.au/site/page.cfm?u=5549
Customs.gov.au wrote:
All goods (except for tobacco products and alcoholic beverages) may be imported duty and tax free if their value is $1,000 or less.
Note: However, where there are multiple packages to the same addressee in Australia from a single consignor overseas that arrive at about the same time, then the value of all packages will be combined for duty and tax assessment purposes. Refer to example 1.
Imported goods with a value of A$1000 or less
Imported goods arriving by post will be released duty and tax free by Customs for delivery direct to the addressee
except for tobacco, tobacco products and alcoholic beverages (refer to example 2) or goods subject to import permit requirements
in these cases, you will be contacted and notified of the action you must take.
Imported goods arriving otherwise than by post will require the completion of a Self Assessed Clearance (SAC) declaration before clearance from Customs control
I'd say the other thing to consider is shipping/postage costs. Get quotes form the suppliers in the UK for what the ex-VAT price pluys shipping will cost, find out the weight (and approx shape/dimensions) and check what your mate's mate will be charged if he does it at the Post Office, often as not the businesses will get it cheaper than an individual. It cost me 40 GBP to send a grille from the UK (and that was the cheapest way possible, by sea).
PS. If it's bits & pieces of small parts and you decide to go the friend-posting route, then get your mate to send them in packages of under 2kg as they can be sent by Royal Mail rather than by ParcelForce, and will cost a lot less for 3 x 2 kg packages than it would for 1 x 6kg package, although be careful of the mention of this in the customs stuff above if the total value is getting towards $1000.