@ asbojohn: A good hint!
Yes, there is a difference, but "only" 7%:
The VAT in Austria is the same than in the U.K.: 20%.
In addition to that there is a tax related with the fuel consumption:
For a 4/4 (avg. 6.4 ltr/100 km) this is 7%, for the +4 (7,3 ltr) 8% and for the Roadster (9.8 ltr) 14%.
With regard to the a.m. example 4/4 this would explain (together with the 5% "lhd surcharge") ~12% difference.
(b.t.w.: I haven't found a rhd price list in GBP. Are the 5% plus for the rhd correct?)
If I take estimated costs for transportation of EUR 1500,- this gives another ~3%.
Where do the remaining 15% come from?
Any ideas or experiences?