Be careful with that one. Wiggle definitely charges in AUD but others like CRC and Ribble give an AUD estimate on their site but still charge in GBP. It will depend on the conversion rate and fees of your CC or paypal as to how close the estimate is to what you pay, it is normally around 2% more than the estimate.
On the topic of good/bad experiences I've had nothing but good experiences with Wiggle, Ribble, CRC, Torpedo7 and Bike Tires Direct. Most have just been straight forward orders with only two exceptions where service was needed.
The first was a faulty tyre from biketiresdirect that had some splitting on the sidewalls within a km of riding. I sent them photos of the splitting and they happily sent a new tyre to replace it, no need to send the faulty tyre back. The replacement was still going along nicely when my wife decided to upgrade from slicks on her MTB to a road bike.
The other time was when I purchased a couple of cycle computers from CRC. Installed one and it went ok on some short rides but on my first ride of over 20km it had freezing issues. I packed it back up and sent it back with the other identical computer I hadn't yet installed on my wife's bike along with their return form and about a week later had the refund back in my account.